media: ar0521: fix error return code in ar0521_power_on()

Return error code if ar0521_write_regs() fails in ar0521_power_on().

Fixes: 852b50ae

 ("media: On Semi AR0521 sensor driver")
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Acked-by: Krzysztof Hałasa <khalasa@piap.pl>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>