libi2c: Mention the correct license in source files

The libi2c library is released under the LGPL, not GPL, as explained
in the README file and documented in lib/Module.mk. Thanks to
Aurelien Jarno for pointing out the inconsistency.

A little bit of history:

The code started its life two decades ago as part of the lm-sensors
project, which was released as a whole under the GPL originally,
including the library part (libsensors).

In 2007, I decided to split the i2c tools, which are not specific
to sensor devices, to a separate package.

In 2009, as I was working on lm-sensors v3, I contacted all the
original authors to get their approval to release the upcoming and all
future versions of libsensors as LGPL instead, to allow wider
adoption. The proposal was accepted by all original authors.

In 2012, I decided to turn the inlined i2c_smbus_* helper functions
into a proper library, with the intent to release it under the LGPL,
as is the common practice for libraries. As the authors of this code
is a subset of the authors of libsensors, I assumed their agreement
for libsensors could be extended to libi2c as well. This is the
reason why LGPL is mentioned in README and lib/Module.mk.

Unfortunately, when working on the library code itself, I forgot to
update the comments in the source files. Let's fix them now.

Signed-off-by: Jean Delvare <jdelvare@suse.de>

include/i2c/smbus.h

@@ -1,23 +1,14 @@
 /*
     smbus.h - SMBus level access helper functions
 
-    Copyright (C) 1995-97 Simon G. Vogl
-    Copyright (C) 1998-99 Frodo Looijaard <frodol@dds.nl>
+    Copyright (C) 1995-1997  Simon G. Vogl
+    Copyright (C) 1998-1999  Frodo Looijaard <frodol@dds.nl>
+    Copyright (C) 2012-2017  Jean Delvare <jdelvare@suse.de>
 
-    This program is free software; you can redistribute it and/or modify
-    it under the terms of the GNU General Public License as published by
-    the Free Software Foundation; either version 2 of the License, or
+    This library is free software; you can redistribute it and/or modify
+    it under the terms of the GNU Lesser General Public License as published
+    by the Free Software Foundation; either version 2.1 of the License, or
     (at your option) any later version.
-
-    This program is distributed in the hope that it will be useful,
-    but WITHOUT ANY WARRANTY; without even the implied warranty of
-    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-    GNU General Public License for more details.
-
-    You should have received a copy of the GNU General Public License
-    along with this program; if not, write to the Free Software
-    Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
-    MA 02110-1301 USA.
 */
 
 #ifndef LIB_I2C_SMBUS_H

lib/smbus.c

@@ -5,20 +5,10 @@
     Copyright (C) 1998-1999  Frodo Looijaard <frodol@dds.nl>
     Copyright (C) 2012-2013  Jean Delvare <jdelvare@suse.de>
 
-    This program is free software; you can redistribute it and/or modify
-    it under the terms of the GNU General Public License as published by
-    the Free Software Foundation; either version 2 of the License, or
+    This library is free software; you can redistribute it and/or modify
+    it under the terms of the GNU Lesser General Public License as published
+    by the Free Software Foundation; either version 2.1 of the License, or
     (at your option) any later version.
-
-    This program is distributed in the hope that it will be useful,
-    but WITHOUT ANY WARRANTY; without even the implied warranty of
-    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-    GNU General Public License for more details.
-
-    You should have received a copy of the GNU General Public License
-    along with this program; if not, write to the Free Software
-    Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
-    MA 02110-1301 USA.
 */
 
 #include <errno.h>