drm/amd/display: validate extended dongle caps

[why]
Some dongle doesn't have a valid extended dongle caps,
but we still set the extended dongle caps to be valid.
This causes validation fails for all timing.

[how]
If no dp_hdmi_max_pixel_clk is provided,
don't use extended dongle caps.
Signed-off-by: Wenjing Liu <Wenjing.Liu@amd.com>
Reviewed-by: Aric Cyr <Aric.Cyr@amd.com>
Reviewed-by: Jun Lei <Jun.Lei@amd.com>
Acked-by: Abdoulaye Berthe <Abdoulaye.Berthe@amd.com>
Acked-by: Leo Li <sunpeng.li@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c

@@ -2247,7 +2247,8 @@ static void get_active_converter_info(
 					translate_dpcd_max_bpc(
 						hdmi_color_caps.bits.MAX_BITS_PER_COLOR_COMPONENT);
 
-				link->dpcd_caps.dongle_caps.extendedCapValid = true;
+				if (link->dpcd_caps.dongle_caps.dp_hdmi_max_pixel_clk != 0)
+					link->dpcd_caps.dongle_caps.extendedCapValid = true;
 			}
 
 			break;