Enable hardware memory error handling for NFS

Truncation of data pages at runtime should be safe in NFS,
even when it doesn't support migration so far.

Trond tells me migration is also queued up for 2.6.32.

Acked-by: Trond.Myklebust@netapp.com
Signed-off-by: Andi Kleen <ak@linux.intel.com>