libpayload: Add fmap_cache to sysinfo_t

Now that FMAP is cached in CBMEM and its pointer is added to coreboot
table for quick lookup, this change adds a new member "fmap_cache" to
sysinfo_t that can be used by payloads to get to FMAP cache.

BUG=b:141723751

Change-Id: If894c20c2de89a9d8564561bc7780c86f3f4135a
Signed-off-by: Furquan Shaikh <furquan@google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/35640
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Shelley Chen <shchen@google.com>
Reviewed-by: Patrick Rudolph <siro@das-labor.org>
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>

payloads/libpayload/include/coreboot_tables.h

@@ -78,6 +78,7 @@ enum {
 	CB_TAG_VBOOT_WORKBUF		= 0x0034,
 	CB_TAG_MMC_INFO			= 0x0035,
 	CB_TAG_TCPA_LOG			= 0x0036,
+	CB_TAG_FMAP			= 0x0037,
 	CB_TAG_CMOS_OPTION_TABLE	= 0x00c8,
 	CB_TAG_OPTION			= 0x00c9,
 	CB_TAG_OPTION_ENUM		= 0x00ca,