mwl8k: Marvell TOPDOG wireless driver

Add a driver for Marvell 88w8xxx TOPDOG PCI/PCIe wireless parts.
This initial version supports the 88w8687 802.11b/g PCIe part on
channels 1-11, and only STA mode is currently implemented.

Signed-off-by: Lennert Buytenhek <buytenh@marvell.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>