Staging: Add stlc45xx, wi-fi driver for stlc4550/4560

This patch adds a new driver called stlc45xx, which supports wi-fi chipsets
stlc4550 and stlc4560 from ST-NXP Wireless. The chipset can be found, for
example, from Nokia N800 and N810 products.

The driver is implemented based on the firmware interface information
published by ST-NXP Wireless here:

http://wireless.kernel.org/en/developers/Documentation/specs#STMicroelectronicshardware

Currently only SPI interface is supported.

Signed-off-by: Kalle Valo <kalle.valo@nokia.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>