x86/build: Tuck away built-in firmware under FW_LOADER

When FW_LOADER is modular or disabled we don't use it.
Update x86 relocs to reflect that.

Reviewed-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
Link: https://lore.kernel.org/r/20211021155843.1969401-7-mcgrof@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>