afs: Use netfslib for symlinks, allowing them to be cached

afs: Use netfslib for symlinks, allowing them to be cached

Use netfslib to read symlinks, thereby allowing them to be cached by
fscache and cachefiles.

Signed-off-by: David Howells <dhowells@redhat.com>
Link: https://lore.kernel.org/r/20241216204124.3752367-23-dhowells@redhat.com
cc: Marc Dionne <marc.dionne@auristor.com>
cc: Jeff Layton <jlayton@kernel.org>
cc: linux-afs@lists.infradead.org
cc: netfs@lists.linux.dev
cc: linux-fsdevel@vger.kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>