rbd: fix -Wreturn-type warnings

/git/arm-soc/drivers/block/rbd.c: In function 'rbd_img_is_write':
/git/arm-soc/drivers/block/rbd.c:1397:1: error: control reaches end of non-void function [-Werror=return-type]
 }
 ^
/git/arm-soc/drivers/block/rbd.c: In function '__rbd_obj_handle_request':
/git/arm-soc/drivers/block/rbd.c:2499:1: error: control reaches end of non-void function [-Werror=return-type]
 }
 ^
/git/arm-soc/drivers/block/rbd.c: In function 'rbd_obj_handle_write':
/git/arm-soc/drivers/block/rbd.c:2471:1: error: control reaches end of non-void function [-Werror=return-type]
 }

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
index 07dc541..9445a71 100644
--- a/drivers/block/rbd.c
+++ b/drivers/block/rbd.c
@@ -1394,6 +1394,7 @@
 	default:
 		rbd_assert(0);
 	}
+	return false;
 }
 
 static void rbd_obj_handle_request(struct rbd_obj_request *obj_req);
@@ -2468,6 +2469,7 @@
 	default:
 		rbd_assert(0);
 	}
+	return true;
 }
 
 /*
@@ -2496,6 +2498,7 @@
 	default:
 		rbd_assert(0);
 	}
+	return true;
 }
 
 static void rbd_obj_end_request(struct rbd_obj_request *obj_req)