Bluetooth: Add btmrvl driver for Marvell Bluetooth devices

This driver provides basic definitions and library functions to
support Marvell Bluetooth enabled devices, such as 88W8688 WLAN/BT
combo chip.

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>