drm/amdkfd: start using tlb_seq from the VM subsystem

Instead of trying to figure out if a TLB flush is necessary or not use
the information provided by the VM subsystem now.

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Philip <Yang&lt;Philip.Yang@amd.com>
Reviewed-by: Felix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>