NFSv4.2: Set the correct size scratch buffer for decoding READ_PLUS

The scratch_buf array is 16 bytes, but I was passing 32 to the
xdr_set_scratch_buffer() function. Fix this by using sizeof(), which is
what I probably should have been doing this whole time.

Fixes: d3b00a80 ("NFS: Replace the READ_PLUS decoding code")
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

fs/nfs/nfs42xdr.c

@@ -1142,7 +1142,7 @@ static int decode_read_plus(struct xdr_stream *xdr, struct nfs_pgio_res *res)
 	if (!segs)
 		return -ENOMEM;
 
-	xdr_set_scratch_buffer(xdr, &scratch_buf, 32);
+	xdr_set_scratch_buffer(xdr, &scratch_buf, sizeof(scratch_buf));
 	status = -EIO;
 	for (i = 0; i < segments; i++) {
 		status = decode_read_plus_segment(xdr, &segs[i]);