arm: mvebu: serial: Add me as co-maintainer and author of Marvell serial drivers

There is no maintainer entry for serial_mvebu_a3700.c. Add entry with Pali
and Stefan as maintainers.

Signed-off-by: Pali Rohár <pali@kernel.org>
Acked-by: Stefan Roese <sr@denx.de>
Reviewed-by: Stefan Roese <sr@denx.de>

drivers/serial/serial_mvebu_a3700.c

@@ -1,6 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0+
 /*
  * Copyright (C) 2016 Stefan Roese <sr@denx.de>
+ * Copyright (C) 2021 Pali Rohár <pali@kernel.org>
  */
 
 #include <common.h>