ecryptfs: remove NULL remount_fs from super_operations

This got missed during the mount API conversion. This makes no functional
difference, but after we convert the last filesystem, we'll want to remove
the remount_fs op from super_operations altogether. So let's just get this
out of the way now.

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Link: https://lore.kernel.org/r/5dc2eb45-7126-4777-a7f9-29d02dff443f@redhat.com


Signed-off-by: Christian Brauner <brauner@kernel.org>