cbmem: add coreboot table records for each cbmem entry

In order to not expose the cbmem data structures to userland
that are used by coreboot internally add each of the cbmem
entries to a coreboot table record. The payload ABI uses
coreboot tables so this just provides a shortcut for cbmem
entries which were manually added previously by doing the
work on behalf of all entries.

A cursor structure and associated functions are added to
the imd code for walking the entries in order to be placed
in the coreboot tables.  Additionally a struct lb_cbmem_entry
is added that lists the base address, size, and id of the
cbmem entry.

BUG=chrome-os-partner:43731
BRANCH=None
TEST=Booted glados. View coreboot table entries with cbmem.

Change-Id: I125940aa1898c3e99077ead0660eff8aa905b13b
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: http://review.coreboot.org/11757
Reviewed-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>
Tested-by: build bot (Jenkins)

src/commonlib/include/commonlib/coreboot_tables.h

@@ -308,6 +308,19 @@ struct lb_boot_media_params {
 	uint64_t boot_media_size;
 };
 
+/*
+ * There can be more than one of these records as there is one per cbmem entry.
+ */
+#define LB_TAG_CBMEM_ENTRY 0x0031
+struct lb_cbmem_entry {
+	uint32_t tag;
+	uint32_t size;
+
+	uint64_t address;
+	uint32_t entry_size;
+	uint32_t id;
+};
+
 #define LB_TAG_SERIALNO		0x002a
 #define MAX_SERIALNO_LENGTH	32