media: ov8856: suppress probe deferral errors

Probe deferral should not be logged as an error:

	ov8856 24-0010: failed to get HW configuration: -517

Use dev_err_probe() for the clock lookup and drop the (mostly) redundant
dev_err() from sensor probe() to suppress it.

Note that errors during regulator lookup is already correctly logged
using dev_err_probe().

Fixes: 0c2c7a1e ("media: ov8856: Add devicetree support")
Cc: stable@vger.kernel.org
Signed-off-by: Johan Hovold <johan+linaro@kernel.org>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>