linux: license files hashes are only valid for latest known version

linux: license files hashes are only valid for latest known version

The content of COPYING changed between v4.16 and v4.17. Since kernels
before and after the change are supported, storing the hash for this
file will cause an error during "make legal-info" when a kernel with the
respective other hash is being used.

So, for the kernel, we do like we did for ATF: the license file is only
listed for the latest version.

In the process, add the missing license files referenced from COPYING
and align the fields to the new spacing convention.

Signed-off-by: Markus Mayer <mmayer@broadcom.com>
[yann.morin.1998@free.fr:
  - only list the licenses files for the latest version
  - restore the hash for COPYING
  - introduce hashes for the two new license files
  - expand commit log accordingly
]
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>