staging: wfx: fix warning about freeing in-use mutex during device unregister

staging: wfx: fix warning about freeing in-use mutex during device unregister

After hif_shutdown(), communication with the chip is no more possible.
It the only request that never reply. Therefore, hif_cmd.lock is never
unlocked. hif_shutdown() unlock itself hif_cmd.lock to avoid a potential
warning during disposal of device. hif_cmd.key_renew_lock should also
been unlocked for the same reason.

Signed-off-by: Jérôme Pouiller <jerome.pouiller@silabs.com>
Link: https://lore.kernel.org/r/20200310101356.182818-2-Jerome.Pouiller@silabs.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>