drm/dp: Add definitons for MSA MISC bits

Add definitions for the MSA (Main Stream Attribute) MISC bits. On
some hardware you can program these directly into a register.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190718145053.25808-2-ville.syrjala@linux.intel.com


Reviewed-by: Gwan-gyeong Mun <gwan-gyeong.mun@intel.com>