SMM: Restore GNVS pointer in the resume path

The SMM GNVS pointer is normally updated only when the
ACPI tables are created, which does not happen in the
resume path.

In order to restore this pointer it needs to be available
at resume time.  The method used to locate it at creation
time cannot be used again as that magic signature is
overwritten with the address itself.  So a new CBMEM ID
is added to store the 32bit address so it can be found
again easily.

A new function is defined to save this pointer in CBMEM
which needs to be called when the ACPI tables are created
in each mainboard when write_acpi_tables() is called.

The cpu_index variable had to be renamed due to a conflict
when cpu/cpu.h is added for the smm_setup_structures()
prototype.

Change-Id: Ic764ff54525e12b617c1dd8d6a3e5c4f547c3e6b
Signed-off-by: Duncan Laurie <dlaurie@chromium.org>
Reviewed-on: http://review.coreboot.org/1765
Tested-by: build bot (Jenkins)
Reviewed-by: Ronald G. Minnich <rminnich@gmail.com>
diff --git a/src/include/cbmem.h b/src/include/cbmem.h
index b43c972..21efe77 100644
--- a/src/include/cbmem.h
+++ b/src/include/cbmem.h
@@ -44,6 +44,7 @@
 #define CBMEM_ID_FREESPACE	0x46524545
 #define CBMEM_ID_GDT		0x4c474454
 #define CBMEM_ID_ACPI		0x41435049
+#define CBMEM_ID_ACPI_GNVS	0x474e5653
 #define CBMEM_ID_CBTABLE	0x43425442
 #define CBMEM_ID_PIRQ		0x49525154
 #define CBMEM_ID_MPTABLE	0x534d5054