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/lib/Makefile.inc

@@ -102,6 +102,9 @@ ramstage-y += b64_decode.c
 romstage-y += cbmem_common.c dynamic_cbmem.c
 ramstage-y += cbmem_common.c dynamic_cbmem.c
 
+romstage-y += imd.c
+ramstage-y += imd.c
+
 ramstage-y += hexdump.c
 romstage-y += hexdump.c