prism54: set netdev type to "wlan"

Userspace uses the netdev devtype for stuff like device naming and type
detection.  Be nice and set it.  Remove the pointless #if/#endif around
SET_NETDEV_DEV too.

Signed-off-by: Dan Williams <dcbw@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: John W. Linville <linville@tuxdriver.com>