Change in coreboot[master]: commonlib: Clean up compiler.h

[Julius Werner (Code Review)]

Attention is currently required from: Philipp Hug, Patrick Georgi, Jakub Czapiga, ron minnich.
Hello Philipp Hug, Patrick Georgi, Jakub Czapiga, Yu-Ping Wu, ron minnich,

I'd like you to reexamine a change. Please visit

https://review.coreboot.org/c/coreboot/+/64737

to look at the new patch set (#4).

Change subject: commonlib: Clean up compiler.h
......................................................................

commonlib: Clean up compiler.h

This patch contains several minor cleanups related to compiler.h:

- Replace __always_unused() (which is a Linux-specific concept that
  doesn't make sense without also having __maybe_unused(), and had zero
  uses in the codebase) with __unused() which moves here from helpers.h

- Add __underscores__ to the names of all attributes in the compiler
  attribute shorthand macros. This is necessary to make them work in
  files where the same name was already used for an identifier (e.g.
  cbfstool/cbfs.h's `unused` array of file types).

- Remove libpayload's own copy of compiler.h and make it directly pull
  in the commonlib/bsd copy.

Signed-off-by: Julius Werner 
Change-Id: I9644da594bb69133843c6b7f12ce50b2e45fd24b
---
M payloads/libpayload/Makefile.inc
M payloads/libpayload/bin/lpgcc
D payloads/libpayload/include/compiler.h
M payloads/libpayload/tests/Makefile.inc
M src/arch/riscv/opensbi.c
M src/commonlib/bsd/include/commonlib/bsd/compiler.h
M src/commonlib/include/commonlib/helpers.h
7 files changed, 20 insertions(+), 69 deletions(-)

git pull ssh://review.coreboot.org:29418/coreboot refs/changes/37/64737/4