This commit fixes all copyright notes, using "git blame" as a
reference. For simple files I just added a 2-lines boilerplate about
being WR and GPL.
Some parts I left untouched:
trivial-init and related files (unclear to me what this is,
and pf-microcode.h is magic binary pfilter values).
tools/lm32-etheruart: I don't know what this is and who the author is
libsdbfs: this comes from another repo and I'd better not change it
sfp_lib.h and hal_shmem.h: I lost track about the origin of this,
among the several packages.
Signed-off-by: Alessandro Rubini <firstname.lastname@example.org>