x86: provide infrastructure to backup default SMM region

Certain CPUs require the default SMM region to be backed up
on resume after a suspend. The reason is that in order to
relocate the SMM region the default SMM region has to be used.
As coreboot is unaware of how that memory is used it needs to
be backed up. Therefore provide a common method for doing this.

Change-Id: I65fe1317dc0b2203cb29118564fdba995770ffea
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: http://review.coreboot.org/5216
Tested-by: build bot (Jenkins)
Reviewed-by: Aaron Durbin <adurbin@google.com>

src/include/cbmem.h

@@ -61,6 +61,7 @@
 #define CBMEM_ID_EHCI_DEBUG	0xe4c1deb9
 #define CBMEM_ID_REFCODE	0x04efc0de
 #define CBMEM_ID_REFCODE_CACHE	0x4efc0de5
+#define CBMEM_ID_SMM_SAVE_SPACE	0x07e9acee
 #define CBMEM_ID_NONE		0x00000000
 #define CBMEM_ID_AGESA_RUNTIME	0x41474553
 #define CBMEM_ID_HOB_POINTER		0x484f4221