drm/amd/display: fix memleak in aconnector->timing_requested

[Why]
when amdgpu_dm_update_connector_after_detect is called
two times successively with valid sink, memory allocated of
aconnector->timing_requested for the first call is not free.
this causes memeleak.

[How]
allocate memory only when aconnector->timing_requested
is null.
Reviewed-by: Qingqing Zhuo <Qingqing.Zhuo@amd.com>
Acked-by: Qingqing Zhuo <qingqing.zhuo@amd.com>
Signed-off-by: Hersen Wu <hersenxs.wu@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c

@@ -3128,9 +3128,12 @@ void amdgpu_dm_update_connector_after_detect(
 						    aconnector->edid);
 		}
 
-		aconnector->timing_requested = kzalloc(sizeof(struct dc_crtc_timing), GFP_KERNEL);
-		if (!aconnector->timing_requested)
-			dm_error("%s: failed to create aconnector->requested_timing\n", __func__);
+		if (!aconnector->timing_requested) {
+			aconnector->timing_requested =
+				kzalloc(sizeof(struct dc_crtc_timing), GFP_KERNEL);
+			if (!aconnector->timing_requested)
+				dm_error("failed to create aconnector->requested_timing\n");
+		}
 
 		drm_connector_update_edid_property(connector, aconnector->edid);
 		amdgpu_dm_update_freesync_caps(connector, aconnector->edid);