[media] s5k6aa: fix sparse warnings

drivers/media/i2c/s5k6aa.c:351:16: warning: cast to restricted __be16
drivers/media/i2c/s5k6aa.c:351:16: warning: cast to restricted __be16
drivers/media/i2c/s5k6aa.c:351:16: warning: cast to restricted __be16
drivers/media/i2c/s5k6aa.c:351:16: warning: cast to restricted __be16

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Acked-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>