drm/amdkfd: Update CU masking for GFX 9.4.3

The CU mask passed from user-space will change based on
different spatial partitioning mode. As a result, update
CU masking code for GFX9.4.3 to work for all partitioning
modes.

Signed-off-by: Mukul Joshi <mukul.joshi@amd.com>
Reviewed-by: Felix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>