drm/amdkfd: Add gws number to kfd topology node properties

Add amdgpu_amdkfd interface to get num_gws and add num_gws
to /sys/class/kfd/kfd/topology/nodes/x/properties. Only report
num_gws if MEC FW support GWS barriers. Currently it is
determined by a module parameter which will be replaced
with MEC FW version check when firmware is ready.

Signed-off-by: Oak Zeng <Oak.Zeng@amd.com>
Reviewed-by: Felix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>