media: i2c: ov5648: fix wrong pointer passed to IS_ERR() and PTR_ERR()

IS_ERR() and PTR_ERR() use wrong pointer, it should be
sensor->dovdd, fix it.

Fixes: e43ccb0a ("media: i2c: Add support for the OV5648 image sensor")
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>