drm/amdgpu: fix aperture mapping leak
In the Linux kernel, the following vulnerability has been resolved: drm/amdgpu: fix aperture mapping leak amdgpu_pci_remove() calls drm_dev_unplug() before invoking the driver fini routines. This causes drm_dev_enter() in amdgpu_ttm_fini() to always return false, so iounmap(aper_base_kaddr) never runs on normal driver unload, leaving an orphaned entry in the x86 PAT interval tree. On connected_to_cpu hardware, the aperture is mapped write-back (WB) via ioremap_cache(). On reload, IP discovery calls memremap(..., MEMREMAP_WC) over the same range. The WC vs WB conflict causes: ioremap error for 0x..., requested 0x1, got 0x0 amdgpu: disc