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/arch/arm/tables.c

@@ -54,3 +54,7 @@ void write_tables(void)
 	/* Print CBMEM sections */
 	cbmem_list();
 }
+
+void lb_arch_add_records(struct lb_header *header)
+{
+}