drm/i915/display: Enable HDR for Parade based lspcon

Enable HDR for LSPCON based on Parade along with MCA.

v2: Added a helper for status reg as suggested by Ville.

v3: Removed a redundant variable, added Ville's RB.

Signed-off-by: Uma Shankar <uma.shankar@intel.com>
Signed-off-by: Vipin Anand <vipin.anand@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201130204738.2443-11-uma.shankar@intel.com