drm/amdkfd: add pasid debugfs entries

the entries will be appearing at
/sys/kernel/debug/kfd/proc/<pid>/pasid_<gpuid>.

Signed-off-by: Eric Huang <jinhuieric.huang@amd.com>
Reviewed-by: Harish Kasiviswanathan <Harish.Kasiviswanathan@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>