drm/amd/display: Fix drm_edid leak in amdgpu_dm

In the Linux kernel, the following vulnerability has been resolved: 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. (cherry picked from commit 52024a94e7111366141cfc5d888b2ef011f879e5)