drm/amdgpu: Fix sdma 4.4.2 doorbell rptr/wptr init

Doorbell rptr/wptr can be set through multiple ways including direct
register initialization. Disable doorbell during hw_fini once the ring
is disabled so that during next module reload direct initialization
takes effect. Also, move the direct initialization after minor update is
set to 1 since rptr/wptr are reinitialized back to 0 which could be
lower than the previous doorbell value (ex: cases like module reload).

Signed-off-by: Lijo Lazar <lijo.lazar@amd.com>
Reviewed-by: Le Ma <le.ma@amd.com>
Reviewed-by: Asad Kamal <asad.kamal@amd.com>
Tested-by: Asad Kamal <asad.kamal@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>