NFS: fix pnfs regression with directio reads

Commit 1abb50886af "NFS: Create an read_pageio_init() function"
did not modify the call in direct.c, preventing direct io from
using pnfs.  This reintroduces that capability.

Signed-off-by: Fred Isaman <iisaman@netapp.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

fs/nfs/direct.c

@@ -393,7 +393,7 @@ static ssize_t nfs_direct_read_schedule_iovec(struct nfs_direct_req *dreq,
 	size_t requested_bytes = 0;
 	unsigned long seg;
 
-	nfs_pageio_init_read(&desc, dreq->inode,
+	NFS_PROTO(dreq->inode)->read_pageio_init(&desc, dreq->inode,
 			     &nfs_direct_read_completion_ops);
 	get_dreq(dreq);
 	desc.pg_dreq = dreq;