drm/radeon: add new INFO ioctl requests

Add requests to get the number of shader engines (SE) and
the number of SH per SE.  These are needed for geometry
and tesselation shaders in the 3D driver as well as setting
up PA_SC_RASTER_CONFIG on SI asics.

Signed-off-by: Alex Deucher <alexander.deucher@amd.com>