Update pixel_rate and link frequency for 1920x1080@30
while changing mode.

Update vblank value while changing mode

Add support to handle multiple link frequencies.

Add dummy ctrl cases for pixel_rate and link frequency
to avoid error while changing the modes dynamically.

Update default link frequency from device tree max link
frequency value.

Update init_cfg() function to update the link frequency
menu_skip_mask value.
Suggested-by: Sakari Ailus <sakari.ailus@iki.fi>
Signed-off-by: Shravan Chippa <shravan.chippa@microchip.com>
[Sakari Ailus: Document menu_skip_mask, remove extra blank line.]
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>