Currently vivid supports V4L2_DV_BT_STD_DMT and V4L2_DV_BT_STD_CEA861
discrete video standards. Extending the capability set to allow for
setting CVT and GTF standards. This change, along with adding the
support for calculating CVT, GTF timings in v4l2-ctl would extend
the number of resolutions supported by vivid to almost any custom
resolution.

Also extending the limits on min and max pixel clock to accommodate
pixel clock range provided by cvt/gtf for resolutions ranging from
640x360p50 to 4kx2Kp60.
Signed-off-by: Prashant Laddha <prladdha@cisco.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>