Some of our files didn't have a copyright notice at all, let's add
it. Also, update the notices in other files and ensure a SPDX
identifier is present in all but the most trivial files.
Change-Id: If7fa19ce484b415bc645e39b3d0d666b44b5f0fd
While in TS 24.007 there is a separate L3 SAPI for GMM and SM,
this only applies to messages sent over LAPDm, and not LLC.
In LLC, both GMM and SM are sent via the same LLGMM LLC-SAPI.
Change-Id: I7814c952cd7f6032222b190d396aaa0570571bfc