disable large folios for shmem file used by xfs xfile

[Christoph Hellwig]

Hi all,

Darrick reported that the fairly new XFS xfile code blows up when force
enabling large folio for shmem.  This series fixes this quickly by disabling
large folios for this particular shmem file for now until it can be fixed
properly, which will be a lot more invasive.

I've added most of you to the CC list as I suspect most other users of
shmem_file_setup and friends will have similar issues.