bootblock: Provide some common prototypes

The split of bootblock initialisation to cpu, northbridge and
southbridge is not specific to intel at all, create new header
<arch/bootblock.h> as AMD will want some of these too.

Change-Id: I702cc6bad4afee4f61acf58b9155608b28eb417e
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/37429
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>

src/northbridge/intel/pineview/bootblock.c

@@ -11,8 +11,8 @@
  * GNU General Public License for more details.
  */
 
+#include <arch/bootblock.h>
 #include <device/pci_ops.h>
-#include <cpu/intel/car/bootblock.h>
 #include "pineview.h"
 
 #define MMCONF_256_BUSSES 16