powerpc/powernv/npu: Remove obsolete comment about TCE_KILL_INVAL_ALL

TCE_KILL_INVAL_ALL has moved long ago but the comment was forgotted so
finish the move and remove the comment.

Fixes: 0bbcdb43 "powerpc/powernv/npu: TCE Kill helpers cleanup"
Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/platforms/powernv/npu-dma.c

@@ -28,10 +28,6 @@
  */
 static DEFINE_SPINLOCK(npu_context_lock);
 
-/*
- * Other types of TCE cache invalidation are not functional in the
- * hardware.
- */
 static struct pci_dev *get_pci_dev(struct device_node *dn)
 {
 	struct pci_dn *pdn = PCI_DN(dn);