cbfstool: fix option parsing

"cbfstool create -B bootblock -s size" (in this order)
would break bootblock selection.

Change-Id: I9a9f5660827c8bf60dae81b519c6f026f3aaa0f3
Found-by: Coverity Scan
Signed-off-by: Patrick Georgi <patrick@georgi-clan.de>
Reviewed-on: http://review.coreboot.org/6564
Reviewed-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>
Reviewed-by: Ronald G. Minnich <rminnich@gmail.com>
Tested-by: build bot (Jenkins)

util/cbfstool/cbfstool.c

@@ -671,6 +671,7 @@ int main(int argc, char **argv)
 				if (tolower(suffix[0])=='m') {
 					param.size *= 1024 * 1024;
 				}
+				break;
 			case 'B':
 				param.bootblock = optarg;
 				break;