loaders: add run_romstage() function to bootblock

Provide a common run_romstage() function to be used by
bootblocks to load and run romstage. This is similar to
run_ramstage() in that it provides a single entry point
for doing the necessary work of loading and running romstage.

Change-Id: Ia9643cc091f97a836cf5caefdff8df4a3443df4c
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: http://review.coreboot.org/8709
Tested-by: build bot (Jenkins)
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>

src/include/program_loading.h

@@ -22,6 +22,12 @@
 #include <stdint.h>
 #include <stddef.h>
 
+/************************
+ *   ROMSTAGE LOADING   *
+ ************************/
+
+/* Run romstage from bootblock. */
+void run_romstage(void);
 
 /************************
  *   RAMSTAGE LOADING   *