lib/coreboot_table: add function to allow arch code to add records

Add lb_arch_add_records() to allow the architecture code to
generically hook into the coreboot table generation.

BUG=chrome-os-partner:50214
BRANCH=glados
TEST=With all subsequent patches confirmed lb_arch_add_records() is
     called when a strong symbol is provided.

Change-Id: I7c69c0ff0801392bbcf5aef586a48388b624afd4
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: https://review.coreboot.org/13669
Tested-by: build bot (Jenkins)
Reviewed-by: Furquan Shaikh <furquan@google.com>
Reviewed-by: Andrey Petrov <andrey.petrov@intel.com>

src/include/boot/coreboot_tables.h

@@ -22,6 +22,9 @@ void lb_board(struct lb_header *header);
 /* Define this in soc or fsp driver to add specific table entries. */
 void lb_framebuffer(struct lb_header *header);
 
+/* Allow arch to add records. */
+void lb_arch_add_records(struct lb_header *header);
+
 /*
  * Function to retrieve MAC address(es) from the VPD and store them in the
  * coreboot table.