NFS: Add a stub for GETDEVICELIST

NFS: Add a stub for GETDEVICELIST

commit 7c61f0d3897eeeff6f3294adb9f910ddefa8035a upstream.

d4b18c3e (pnfs: remove GETDEVICELIST implementation) removed the
GETDEVICELIST operation from the NFS client, but left a "hole" in the
nfs4_procedures array.  This caused /proc/self/mountstats to report an
operation named "51" where GETDEVICELIST used to be.  This patch adds a
stub to fix mountstats.

Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
Fixes: d4b18c3e (pnfs: remove GETDEVICELIST implementation)
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>