wl12xx: enter forced-psm on fw change

Enter forced psm when changing fw, in order to make the
sta a bit more disconnection-persistent.
(DPM doesn't know about the incoming recovery, so it
won't enter psm by itself)

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