media: i2c: ov7251: Introduce 1 ms delay between regulators and en GPIO

Lift the xshutdown (enable) GPIO 1 ms after enabling the regulators, as
required by the sensor's power-up sequence.

Fixes: d30bb512 ("media: Add a driver for the ov7251 camera sensor")
Cc: stable@vger.kernel.org
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Reviewed-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>