staging: most: v4l2-aim: fix interrupt unsafe spinlocks

The functions get_aim_dev() and aim_rx_data() are using interrupt unsafe
spinlocks even though they may be called from an interrupt context.

This patch fixes the described problem.

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