wlcore: remove unnecessary WARN_ON in wl12xx_tx_reset

Sometimes the driver can perform a recovery while Tx is
active, this will trigger unnecessary warning which might
delay the recovery for more than 100 mS.

Signed-off-by: Victor Goldenshtein <victorg@ti.com>
Signed-off-by: Arik Nemtsov <arik@wizery.com>
Signed-off-by: Luciano Coelho <coelho@ti.com>