To support HSA on KV, we need to limit the number of vmids and pipes
that are available for radeon's use with KV.

This patch reserves VMIDs 8-15 for amdkfd (so radeon can only use VMIDs
0-7) and also makes radeon thinks that KV has only a single MEC with a single
pipe in it

v3: Use define for static vmid allocation in radeon
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Oded Gabbay <oded.gabbay@amd.com>