MAINTAINERS: change maintainer of the wl1251 driver

MAINTAINERS: change maintainer of the wl1251 driver

Kalle Valo has asked me to take over the maintenance of the wl1251
driver.  Thanks Kalle for all his work on the wl1251 driver, I'll try
to keep up with his good work from now on.

At the same time, update the Web URL to something more specific.
There's not much in that page, but we will try to update it soon.

Signed-off-by: Luciano Coelho <coelho@ti.com>
Acked-by: Kalle Valo <kvalo@adurom.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>