drm/amdkfd: Query vmid pasid mapping through stored info for non HWS

Because we record the mapping under non HWS mode in the software,
we can query pasid through vmid using the stored mapping instead of
reading from ATC registers.

This also prepares for the defeatured ATC block in future ASICs.

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