mboxd_msg: Remove unreachable break statement

Change-Id: Iaa73c1c02286f9f706e45eda8c1e45f3aa346675
Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
diff --git a/mboxd_msg.c b/mboxd_msg.c
index cdd8b69..d02e0bf 100644
--- a/mboxd_msg.c
+++ b/mboxd_msg.c
@@ -265,7 +265,6 @@
 	default:
 		MSG_ERR("API Version Not Valid - Invalid System State\n");
 		return -MBOX_R_SYSTEM_ERROR;
-		break;
 	}
 
 	return 0;