wl12xx: Use dev_hlid for auth and assoc req

On roaming, the auth and assoc req are sent with the sta
hlid. This is wrong, as the sta hlid is configured according
to the old ap. Use the dev_hlid instead.

Move the wl1271_tx_update_filters() call into wl1271_tx_get_hlid(),
so wl->dev_hlid will be valid.

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