Bluetooth: Add Marvell BT-over-SDIO driver

This driver supports Marvell Bluetooth enabled devices with SDIO
interface. Currently only SD8688 chip is supported.

The helper/firmware images of SD8688 can be downloaded from this tree:
git://git.infradead.org/users/dwmw2/linux-firmware.git



This patch incorporates a lot of comments given by
Nicolas Pitre <nico@marvell.com>. Many thanks to Nicolas Pitre.

Signed-off-by: Rahul Tank <rahult@marvell.com>
Signed-off-by: Bing Zhao <bzhao@marvell.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>