This allows us to query certain registers from userspace
for profiling and harvest configuration.  E.g., it can
be used by the GALLIUM_HUD for profiling the status of
various gfx blocks.
Tested-by: Marek Olšák <marek.olsak@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>