drm/amdkfd: Insert missing TLB flush on GFX10 and later

Heavy-weight TLB flush is required after unmap on all GPUs for
correctness and security.

Signed-off-by: Harish Kasiviswanathan <Harish.Kasiviswanathan@amd.com>
Reviewed-by: Felix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org