coreboot: add imd library

The imd (internal memory database) library provides a way to
track memory regions by assigning ids to each region. The implementation
is a direct descendant of dynamic cbmem. The intent is to replace
the existing mechanisms which do similar things: dynamic cbmem, stage
cache, etc.

Differences between dynamic cbmem and imd:
- All structures/objects are relative to one another. There
  are no absolute pointers serialized to memory.
- Allow limiting the size of the idm. i.e. provide a maximum
  memory usage.
- Allow setting the size of the root structure which allows
  control of the number of allocations to track.

Change-Id: Id7438cff80d396a594d6a7330d09b45bb4fedf2e
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: http://review.coreboot.org/8621
Tested-by: build bot (Jenkins)
Reviewed-by: Marc Jones <marc.jones@se-eng.com>

src/include/cbmem.h

@@ -57,6 +57,7 @@
 #define CBMEM_ID_GDT		0x4c474454
 #define CBMEM_ID_HOB_POINTER	0x484f4221
 #define CBMEM_ID_IGD_OPREGION	0x4f444749
+#define CBMEM_ID_IMD_ROOT	0xff4017ff
 #define CBMEM_ID_MEMINFO	0x494D454D
 #define CBMEM_ID_MPTABLE	0x534d5054
 #define CBMEM_ID_MRCDATA	0x4d524344
@@ -103,6 +104,7 @@ struct cbmem_id_to_name {
 	{ CBMEM_ID_ELOG,		"ELOG       " }, \
 	{ CBMEM_ID_FREESPACE,		"FREE SPACE " }, \
 	{ CBMEM_ID_GDT,			"GDT        " }, \
+	{ CBMEM_ID_IMD_ROOT,		"IMD ROOT   " }, \
 	{ CBMEM_ID_MEMINFO,		"MEM INFO   " }, \
 	{ CBMEM_ID_MPTABLE,		"SMP TABLE  " }, \
 	{ CBMEM_ID_MRCDATA,		"MRC DATA   " }, \