wlcore: set active psm on association

The default ps mode of the fw is auto, while the default
ps mode of mac80211 is active (ps off).
In order to sync them, configure active ps on association.

Signed-off-by: Eliad Peller <eliad@wizery.com>
Reviewed-by: Arik Nemtsov <arik@wizery.com>
Signed-off-by: Luciano Coelho <coelho@ti.com>