netfs: Remove some extraneous directory invalidations

In the directory editing code, we shouldn't re-invalidate the directory
if it is already invalidated.

Signed-off-by: David Howells <dhowells@redhat.com>
Link: https://lore.kernel.org/r/20241216204124.3752367-15-dhowells@redhat.com


cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
Signed-off-by: Christian Brauner <brauner@kernel.org>