wl1251: add support for PG11 chips.

This simple patch adds support for the PG11 variant of the WL1251 chip as
used on the OpenPandora OMAP3 device.

Signed-off-by: David-John Willis <John.Willis@Distant-earth.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>