drm/amdgpu: Fix initial validation of PD BO for KFD VMs

Make sure the PD BO is valid and attach the eviction fence during VM
creation. This ensures that the pd_phys_address is actually valid
and an eviction that would invalidate it triggers a KFD process
eviction like it should.

v2: Use uninterruptible waiting in initial PD validation

Signed-off-by: Felix Kuehling <Felix.Kuehling@amd.com>
Acked-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Oded Gabbay <oded.gabbay@gmail.com>