Bluetooth: hci_mrvl: Add serdev support

This adds serdev support to the Marvell hci uart driver. Only basic
serdev support, none of the fancier features like regulator or enable
GPIO support is added for now.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>