NFS: Fix a compile warning about unused variable in nfs_generic_pg_pgios()

Signed-off-by: NTrond Myklebust <trond.myklebust@primarydata.com>

fs/nfs/pagelist.c

@@ -796,12 +796,9 @@ EXPORT_SYMBOL_GPL(nfs_generic_pgio);
 
 static int nfs_generic_pg_pgios(struct nfs_pageio_descriptor *desc)
 {
-	struct nfs_pgio_mirror *mirror;
 	struct nfs_pgio_header *hdr;
 	int ret;
 
-	mirror = nfs_pgio_current_mirror(desc);
-
 	hdr = nfs_pgio_header_alloc(desc->pg_rw_ops);
 	if (!hdr) {
 		desc->pg_error = -ENOMEM;