arch/x86/bootblock: Do not include non-code files in bootblock.S

Since we now have more freedom in the bootblock linking step it no
longer makes sense to use a monolithic bootblock.S. Code segments must
still be included as the order in bootblock.S determines code flow.
However, non-code flow related assembly stubs don't need to be directly
included in bootblock.S

Change-Id: I08e86e92d82bd2138194ed42652f268b0764aa54
Signed-off-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>
Reviewed-on: http://review.coreboot.org/11792
Tested-by: build bot (Jenkins)
Tested-by: Raptor Engineering Automated Test Stand <noreply@raptorengineeringinc.com>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>

src/arch/x86/Makefile.inc

@@ -84,6 +84,7 @@ endif
 # Add the assembly file that pulls in the rest of the dependencies in
 # the right order. Make sure the auto generated bootblock.inc is a proper
 # dependency. Make the same true for the linker sript.
+bootblock-y += id.S
 bootblock-y += bootblock.S
 bootblock-y += walkcbfs.S
 $(obj)/arch/x86/bootblock.bootblock.o: $(objgenerated)/bootblock.inc