drm/amdgpu: Enable doorbell selfring after resize FB BAR

[Why]
The selfring doorbell aperture will change when resize FB
BAR successfully during gmc sw init, we should reorder
the sequence of enabling doorbell selfring aperture.

[How]
Move enable_doorbell_selfring_aperture from *_common_hw_init
to *_common_late_init.

This fixes the potential issue that GPU ring its own
doorbell when this device is in translated mode when
iommu is on.

v2: Remove *_enable_doorbell_aperture functions (Christian)
v3: Add comments to note that why we need enable doorbell
    selfring late (Christian)

Signed-off-by: Shane Xiao <shane.xiao@amd.com>
Signed-off-by: Aaron Liu <aaron.liu@amd.com>
Tested-by: Xiaomeng Hou <Xiaomeng.Hou@amd.com>
Reviewed-by: Christian K�nig <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>