[media] atmel-isc: remove the warning

Replace the 'IS_ERR_VALUE(irq)' with 'ret < 0' in
function 'atmel_isc_probe'.

Reported-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Songjun Wu <songjun.wu@microchip.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>