cpu/x86: remove BACKUP_DEFAULT_SMM_REGION option

Unconditionally provide the backup default SMM area API. There's no
reason to guard the symbols behind anything since linker garbage
collection is implemented. A board or chipset is free to use the
code or not without needing to select an option.

Change-Id: I14cf1318136a17f48ba5ae119507918190e25387
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: https://review.coreboot.org/14561
Tested-by: build bot (Jenkins)
Reviewed-by: Martin Roth <martinroth@google.com>
9 files changed