drm/dp: DRM DP helper for reading Ignore MSA from DPCD

DP sink device sets the Ignore MSA bit in its
DP_DOWNSTREAM_PORT_COUNT register to indicate its ability to
ignore the MSA video timing parameters and its ability to support
seamless video timing change over a range of timing exposed by
DisplayID and EDID.
This is required for the sink to indicate that it is Adaptive sync
capable.

v3:
* Fi the typo in commit message (Manasi)
v2:
* Rename to describe what the function does (Jani Nikula)

Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Harry Wentland <harry.wentland@amd.com>
Cc: Nicholas Kazlauskas <Nicholas.Kazlauskas@amd.com>
Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200619212356.19285-2-bhanuprakash.modem@intel.com

include/drm/drm_dp_helper.h

@@ -1324,6 +1324,14 @@ drm_dp_alternate_scrambler_reset_cap(const u8 dpcd[DP_RECEIVER_CAP_SIZE])
 			DP_ALTERNATE_SCRAMBLER_RESET_CAP;
 }
 
+/* Ignore MSA timing for Adaptive Sync support on DP 1.4 */
+static inline bool
+drm_dp_sink_can_do_video_without_timing_msa(const u8 dpcd[DP_RECEIVER_CAP_SIZE])
+{
+	return dpcd[DP_DOWN_STREAM_PORT_COUNT] &
+		DP_MSA_TIMING_PAR_IGNORED;
+}
+
 /*
  * DisplayPort AUX channel
  */