media: ov6650: Fix sensor possibly not detected on probe

commit 933c1320 upstream.

After removal of clock_start() from before soc_camera_init_i2c() in
soc_camera_probe() by commit 9aea470b ("[media] soc-camera: switch
I2C subdevice drivers to use v4l2-clk") introduced in v3.11, the ov6650
driver could no longer probe the sensor successfully because its clock
was no longer turned on in advance.  The issue was initially worked
around by adding that missing clock_start() equivalent to OMAP1 camera
interface driver - the only user of this sensor - but a propoer fix
should be rather implemented in the sensor driver code itself.

Fix the issue by inserting a delay between the clock is turned on and
the sensor I2C registers are read for the first time.

Tested on Amstrad Delta with now out of tree but still locally
maintained omap1_camera host driver.

Fixes: 9aea470b ("[media] soc-camera: switch I2C subdevice drivers to use v4l2-clk")

Signed-off-by: Janusz Krzysztofik <jmkrzyszt@gmail.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
[bwh: Backported to 3.16: adjust filename]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>