media: i2c: rdacm21: Power up OV10640 before OV490

The current RDACM21 initialization routine powers up the OV10640 image
sensor after the OV490 ISP. The ISP is programmed with a firmware loaded
from an embedded serial flash that (most probably) tries to interact and
program also the image sensor connected to the ISP.

As described in commit "media: i2c: rdacm21: Fix OV10640 powerup" the
image sensor powerdown signal is kept high by an internal pull up
resistor and occasionally fails to startup correctly if the powerdown
line is not asserted explicitly. Failures in the OV10640 startup causes
the OV490 firmware to fail to boot correctly resulting in the camera
module initialization to fail consequentially.

Fix this by powering up the OV10640 image sensor before testing the
OV490 firmware boot completion, by splitting the ov10640_initialize()
function in an ov10640_power_up() one and an ov10640_check_id() one.

Also make sure the OV10640 identification procedure gives enough time to
the image sensor to resume after the programming phase performed by the
OV490 firmware by repeating the ID read procedure.

This commit fixes a sporadic start-up error triggered by a failure to
detect the OV490 firmware boot completion:
rdacm21 8-0054: Timeout waiting for firmware boot

[hverkuil: fixed two typos in commit log]

Fixes: a59f853b ("media: i2c: Add driver for RDACM21 camera module")
Signed-off-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>