drm/amdgpu: Add early fini callback

Use it to call disply code dependent on device->drv_data
before it's set to NULL on device unplug

v5:
Move HW finilization into this callback to prevent MMIO accesses
post cpi remove.

v7:
Split kfd suspend from device exit to expdite HW related
stuff to amdgpu_pci_remove

v8:
Squash previous KFD commit into this commit to avoid compile break.

Signed-off-by: Andrey Grodzovsky <andrey.grodzovsky@amd.com>
Acked-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Felix Kuehling <Felix.Kuehling@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210520032057.497334-1-andrey.grodzovsky@amd.com