wl12xx: optimise elp wakeup and sleep calls

The wakeup call was done too deep in code path, it's better to wakeup
chip from higher levels. This will also reduce wakeup calls significantly.

Signed-off-by: Kalle Valo <kalle.valo@nokia.com>
Reviewed-by: Luciano Coelho <luciano.coelho@nokia.com>
Signed-off-by: Luciano Coelho <luciano.coelho@nokia.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>