CVE-2024-27041

In the Linux kernel, the following vulnerability has been resolved:

drm/amd/display: fix NULL checks for adev->dm.dc in amdgpudmfini()

Since 'adev->dm.dc' in amdgpudmfini() might turn out to be NULL before the call to dcenabledmub_notifications(), check beforehand to ensure there will not be a possible NULL-ptr-deref there.

Also, since commit 1e88eb1b2c25 ("drm/amd/display: Drop CONFIGDRMAMDDCHDCP") there are two separate checks for NULL in 'adev->dm.dc' before dcdeinitcallbacks() and dcdmubsrv_destroy(). Clean up by combining them all under one 'if'.

Found by Linux Verification Center (linuxtesting.org) with static analysis tool SVACE.