drm/amdgpu: fix waiting for all submissions for userptrs

drm/amdgpu: fix waiting for all submissions for userptrs

Wait for all submissions when userptrs need to be invalidated by the MMU
notifier, not just the one the userptr was involved into.

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Vitaly Prosyak <vitaly.prosyak@amd.com>
Tested-by: Vitaly Prosyak <vitaly.prosyak@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>