drm/amdgpu: Adjust debugfs eviction and IB access permissions

commit f790a2c4 upstream.

Users should not be able to run these.

Reviewed-by: Yang Wang <kevinyang.wang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit 7ba93954)
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>