Fix smatch warning:

drivers/media/i2c/s5k6a3.c:234 __s5k6a3_power_on() warn: 'sensor->clock' from clk_prepare_enable() not released on lines: 234.
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Acked-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>