This patch defines the DP DSC receiver capability size that gives
total number of DP DSC DPCD registers.
This also adds a missing #defines for DP DSC support missed in the
commit id (ab6a46ea "Add DPCD definitions for DP 1.4 DSC feature")

v3:
* MIN_SLICE_WIDTH = 2560 (Anusha)
* Define DP_DSC_SLICE_WIDTH_MULTIPLIER = 320
v2:
* Add SHIFT define and DECOMPRESSION_EN define missed in prev patch

Cc: dri-devel@lists.freedesktop.org
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
Cc: Anusha Srivatsa <anusha.srivatsa@intel.com>
Cc: Gaurav K Singh <gaurav.k.singh@intel.com>
Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
Acked-by: Sean Paul <seanpaul@chromium.org> (For merging through
drm-intel)
Reviewed-by: Anusha Srivatsa <anusha.srivatsa@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20181031001923.31442-2-manasi.d.navare@intel.com