media: atmel-isc: Add spin lock for clock enable ops

Add the spin lock for the clock enable and disable operations.

Signed-off-by: Wenyou Yang <wenyou.yang@microchip.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>