drm/dp: Define payload size for DP SDP PPS packet

DP 1.4 spec defines DP secondary data packet for DSC
picture parameter set. This patch defines its payload size
according to the DP 1.4 specification.
Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
Cc: dri-devel@lists.freedesktop.org
Cc: Gaurav K Singh <gaurav.k.singh@intel.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
Cc: Anusha Srivatsa <anusha.srivatsa@intel.com>
Acked-by: Sean Paul <seanpaul@chromium.org> (For merging through
drm-intel)
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20181031001923.31442-7-manasi.d.navare@intel.com

include/drm/drm_dp_helper.h

@@ -1050,6 +1050,7 @@ struct dp_sdp_header {
 
 #define EDP_SDP_HEADER_REVISION_MASK		0x1F
 #define EDP_SDP_HEADER_VALID_PAYLOAD_BYTES	0x1F
+#define DP_SDP_PPS_HEADER_PAYLOAD_BYTES_MINUS_1 0x7F
 
 struct edp_vsc_psr {
 	struct dp_sdp_header sdp_header;