drm/i915: Add N & CTS values for 10/12 bit deep color

Adding N & CTS values for 10/12 bit deep color from Appendix C
table in HDMI 2.0 spec. The correct values for N is not chosen
automatically by hardware for deep color modes.

v2: Remove unnecessary initialization of size

Signed-off-by: Aditya Swarup <aditya.swarup@intel.com>
Cc: Clint Taylor <Clinton.A.Taylor@intel.com>
Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190627220708.31700-2-aditya.swarup@intel.com