media: adv7604: extend deep color mode to ADV7611

The AD7611 chip supports the same Deep Color Mode settings as the AD7604.
This change extends support for this feature to the AD7611 by adding a
wrapper function for the `read_hdmi_pixelclock` hook and adding the same
frequency adjustment logic.

Signed-off-by: Dragos Bogdan <dragos.bogdan@analog.com>
Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>