drm/dp: Rename the edp_sdp_header as dp_sdp_header

No functional changes in this patch.

The SDP Header is a generic header for secondary data packets for
both eDP and DP so call it dp_sdp_header. This header gets used for
different SDP types already defined.
Also header bytes 2 and 3 are secondary data packet specific header bytes.
So change the comment to indicate the same.

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Jani Nikula <jani.nikula@intel.com>
Cc: dri-devel@lists.freedesktop.org
Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1524770868-16869-1-git-send-email-manasi.d.navare@intel.com

include/drm/drm_dp_helper.h

@@ -967,18 +967,18 @@ int drm_dp_bw_code_to_link_rate(u8 link_bw);
 #define DP_SDP_VSC_EXT_CEA		0x21 /* DP 1.4 */
 /* 0x80+ CEA-861 infoframe types */
 
-struct edp_sdp_header {
+struct dp_sdp_header {
 	u8 HB0; /* Secondary Data Packet ID */
 	u8 HB1; /* Secondary Data Packet Type */
-	u8 HB2; /* 7:5 reserved, 4:0 revision number */
-	u8 HB3; /* 7:5 reserved, 4:0 number of valid data bytes */
+	u8 HB2; /* Secondary Data Packet Specific header, Byte 0 */
+	u8 HB3; /* Secondary Data packet Specific header, Byte 1 */
 } __packed;
 
 #define EDP_SDP_HEADER_REVISION_MASK		0x1F
 #define EDP_SDP_HEADER_VALID_PAYLOAD_BYTES	0x1F
 
 struct edp_vsc_psr {
-	struct edp_sdp_header sdp_header;
+	struct dp_sdp_header sdp_header;
 	u8 DB0; /* Stereo Interface */
 	u8 DB1; /* 0 - PSR State; 1 - Update RFB; 2 - CRC Valid */
 	u8 DB2; /* CRC value bits 7:0 of the R or Cr component */