drm/radeon: Update radeon_info_ioctl for SI. (v2)

v2: agd5f: add new MAX_PIPES param

Signed-off-by: Michel Dänzer <michel.daenzer@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>