drm/amdgpu: remove redundant GPU reset

Because bad pages saving has been moved to UMC error interrupt callback,
which will trigger a new GPU reset after saving.

Signed-off-by: Dennis Li <Dennis.Li@amd.com>
Reviewed-by: Hawking Zhang <hawking.zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>