plat: fix switch statements to comply with MISRA rules

Ensure (where possible) that switch statements in plat comply with MISRA
rules 16.1 - 16.7.

Change-Id: Ie4a7d2fd10f6141c0cfb89317ea28a755391622f
Signed-off-by: Jonathan Wright <jonathan.wright@arm.com>
diff --git a/plat/rpi3/rpi3_bl2_setup.c b/plat/rpi3/rpi3_bl2_setup.c
index 1fd822e..86c66d0 100644
--- a/plat/rpi3/rpi3_bl2_setup.c
+++ b/plat/rpi3/rpi3_bl2_setup.c
@@ -83,6 +83,9 @@
 		bl_mem_params->ep_info.spsr = rpi3_get_spsr_for_bl33_entry();
 		break;
 
+	default:
+		/* Do nothing in default case */
+		break;
 	}
 
 	return err;