media: i2c: adv748x: reuse power up sequence when initializing CSI-2

Extend the MIPI CSI-2 power up sequence to match the power up sequence
in the hardware manual chapter "9.5.1 Power Up Sequence". This change
allows the power up functions to be reused when initializing the
hardware reducing code duplicating as well aligning with the
documentation.

Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Tested-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>