drm/amd/display: Fix drm_edid leak in amdgpu_dm

[WHAT]
When a sink is connected, aconnector->drm_edid was overwritten without
freeing the previous allocation, causing a memory leak on resume.

[HOW]
Free the previous drm_edid before updating it.

Reviewed-by: Roman Li <roman.li@amd.com>
Signed-off-by: Alex Hung <alex.hung@amd.com>
Signed-off-by: Chuanyu Tseng <chuanyu.tseng@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit 52024a9)
Cc: stable@vger.kernel.org

Author: Alex Hung

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

@@ -3909,8 +3909,9 @@ void amdgpu_dm_update_connector_after_detect(
 
 		aconnector->dc_sink = sink;
 		dc_sink_retain(aconnector->dc_sink);
+		drm_edid_free(aconnector->drm_edid);
+		aconnector->drm_edid = NULL;
 		if (sink->dc_edid.length == 0) {
-			aconnector->drm_edid = NULL;
 			hdmi_cec_unset_edid(aconnector);
 			if (aconnector->dc_link->aux_mode) {
 				drm_dp_cec_unset_edid(&aconnector->dm_dp_aux.aux);