staging: wfx: unlock on error path

We need to release the tx_lock on the error path before returning.

Fixes: d1c015b4 ("staging: wfx: rewrite wfx_hw_scan()")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Cc: stable <stable@vger.kernel.org>
Reviewed-by: Jérôme Pouiller <jerome.pouiller@silabs.com>
Link: https://lore.kernel.org/r/20200512083656.GA251760@mwanda


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>