drm/dsc: Define the DSC 1.1 and 1.2 Line Buffer depth constants

DSC specification defines linebuf_depth which contains the
line buffer bit depth used to generate the bitstream.
These values are defined as per Table 4.1 in DSC 1.2 spec

v2 (From Manasi):
* Rename as MAX_LINEBUF_DEPTH for DSC 1.1 and DSC 1.2

Cc: dri-devel@lists.freedesktop.org
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: 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/20181127214125.17658-6-manasi.d.navare@intel.com