media: ti-vpe: cal: use v4l2_get_link_freq

CAL driver uses V4L2_CID_PIXEL_RATE to get the required pixel rate, and
then changes that value to link rate before configuring the registers.

Rewrite the code to use v4l2_get_link_freq(), which simplifies the code
as we get the link rate directly, and it also adds support for
V4L2_CID_LINK_FREQ.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>