Clarify licenses

Libiio was always meant to be LGPL, but the tools, examples and IIOD
were supposed to be GPL (as it does not really make sense for them to
use LGPL).

However, the SPDX identifiers (and the comment blocks before that) of
the source files all stated that the license was LGPL, since the
beginning.

Since re-licensing would be quite a headache, because of the huge number
of copyright holders, simply embrace the mistake and use the LGPL
license for everything.

Signed-off-by: Paul Cercueil <paul@crapouillou.net>

README.md

@@ -6,8 +6,7 @@ libiio is used to interface to the Linux Industrial Input/Output (IIO) Subsystem
 
 Although libiio was primarily developed by Analog Devices Inc., it is an active open source library, which many people have contributed to. The library is released under the GNU Lesser General Public License (LGPL), version 2.1 or (at your option) any later version, this open-source license allows anyone to use the library, on any vendors processor/FPGA/SoC, which may be controlling any vendors peripheral device (ADC, DAC, etc) either locally or remotely. This includes closed or open-source, commercial or non-commercial applications (subject to the LGPL license freedoms, obligations and restrictions). The examples and test applications (sometimes referred to as the iio-utils) are released separately under the GNU General Public License (GPL) version 2.0 (at your option) any later version.
 
-Library License : [![Library License](https://img.shields.io/badge/license-LGPL2+-blue.svg)](https://github.com/analogdevicesinc/libiio/blob/master/COPYING.txt)
-Tests/Examples License : [![Application License](https://img.shields.io/badge/license-GPL2+-blue.svg)](https://github.com/analogdevicesinc/libiio/blob/master/COPYING_GPL.txt)
+Library/Tests/Examples/IIOD License : [![Libiio License](https://img.shields.io/badge/license-LGPL2+-blue.svg)](https://github.com/analogdevicesinc/libiio/blob/master/COPYING.txt)
 Latest Release : [![GitHub release](https://img.shields.io/github/release/analogdevicesinc/libiio.svg)](https://github.com/analogdevicesinc/libiio/releases/latest)
 Downloads :  [![Github All Releases](https://img.shields.io/github/downloads/analogdevicesinc/libiio/total.svg)](https://github.com/analogdevicesinc/libiio/releases/latest)