drm/i915/dsc/mtl: Update the DSC minor version

From MTL onwards we support DSC 1.2, since there is hardcoding to minor
version 1, update it.

Cc: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
Signed-off-by: Vandita Kulkarni <vandita.kulkarni@intel.com>
Reviewed-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220817124516.284456-1-jani.nikula@intel.com