Staging: most: fix double unlock

This patch fixes double unlocking of a spinlock the aim-v4l2 module.

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Christian Gromm <christian.gromm@microchip.com>
Signed-off-by: Andrey Shvetsov <andrey.shvetsov@k2l.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>