LICENSES: Add the LGPL 2.0 license

Add the full text of the LGPL 2.0 license to the kernel tree.  It was
copied directly from:

   https://spdx.org/licenses/LGPL-2.0.html#licenseText

Add the required tags for reference and tooling.
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Reviewed-by: NPhilippe Ombredanne <pombredanne@nexb.com>
Reviewed-by: NKate Stewart <kstewart@linuxfoundation.org>
Reviewed-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NJonathan Corbet <corbet@lwn.net>