drm/dp: add some new DPCD macros from DP 2.0 E11

Add some of the new additions from DP 2.0 E11.

Cc: Uma Shankar <uma.shankar@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://patchwork.freedesktop.org/patch/msgid/ec9c1b94858de36b9f4ef6c197effa4ca667afc3.1643878928.git.jani.nikula@intel.com