dm: core: Drop ofnode_is_available()

This function is also available as ofnode_is_enabled(), so use that
instead.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/net/fec_mxc.c b/drivers/net/fec_mxc.c
index 8bc2b46..bbc4434 100644
--- a/drivers/net/fec_mxc.c
+++ b/drivers/net/fec_mxc.c
@@ -1078,7 +1078,7 @@
 		return ret;
 	}
 
-	if (!ofnode_is_available(phandle_args.node))
+	if (!ofnode_is_enabled(phandle_args.node))
 		return -ENOENT;
 
 	priv->phy_of_node = phandle_args.node;