drm/dp: Add defines for DP SDP types

Add defines for the secondary data packet (SDP) types from the spec.
These are the DP specific ones, and in addition HDMI infoframe types
(see enum hdmi_infoframe_type) are also valid SDP types.

v2: Add more SDP types
v3: Note the DP version that added each SDP type (Rodrigo)

Cc: dri-devel@lists.freedesktop.org
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20170818134958.15502-2-ville.syrjala@linux.intel.com