NFS: Revalidate the file mapping on all fatal writeback errors

If a write or commit failed, and the mapping sees a fatal error, we
need to revalidate the contents of that mapping.

Fixes: 06c9fdf3 ("NFS: On fatal writeback errors, we need to call nfs_inode_remove_request()")
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>