Ask device connected on sink pad for link frequency
in order to configure CLK_LANE_REG1 (ui_x4).
If not available, ask for pixel rate information to compute it.

This is needed to deal with compressed format such as JPEG
where number of bits per pixel is unknown: computation of
link frequency from pixel rate is not possible.
Signed-off-by: Hugues Fruchet <hugues.fruchet@st.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>