staging: vt6656: remove RX complete locking.

The lock in vnt_submit_rx_urb_complete is blocked by TX activity.

The lock comes from a time when RX needed to be synchronized with
other parts of the driver because the WLAN API was in driver.

Since this is now dealt with in mac80211 the lock is unnecessary.

Signed-off-by: Malcolm Priestley <tvboxspy@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>