drm/amdgpu: information leak in amdgpu_info_ioctl()

We recently changed the drm_amdgpu_info_device struct so now there is
a 4 byte hole at the end.  We need to initialize it so we don't disclose
secret information from the stack.

Fixes: fa92754e ('drm/amdgpu: add VCE harvesting instance query')
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>