slimbus: messaging: Fix fall-through warnings for Clang

In preparation to enable -Wimplicit-fallthrough for Clang, fix a warning
by explicitly adding a break statement instead of letting the code fall
through to the next case.

Link: https://github.com/KSPP/linux/issues/115
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Link: https://lore.kernel.org/r/20201127102451.17114-5-srinivas.kandagatla@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/slimbus/messaging.c

@@ -258,6 +258,7 @@ int slim_xfer_msg(struct slim_device *sbdev, struct slim_val_inf *msg,
 	case SLIM_MSG_MC_REQUEST_CLEAR_INFORMATION:
 	case SLIM_MSG_MC_CLEAR_INFORMATION:
 		txn->rl += msg->num_bytes;
+		break;
 	default:
 		break;
 	}