stmmac: make function tables const

These tables only contain function pointers.

Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Acked-by: Gustavo F. Padovan <padovan@profusion.mobi>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/stmmac/enh_desc.c b/drivers/net/stmmac/enh_desc.c
index 5d1471d..e5dfb6a 100644
--- a/drivers/net/stmmac/enh_desc.c
+++ b/drivers/net/stmmac/enh_desc.c
@@ -318,7 +318,7 @@
 	return p->des01.erx.frame_length;
 }
 
-struct stmmac_desc_ops enh_desc_ops = {
+const struct stmmac_desc_ops enh_desc_ops = {
 	.tx_status = enh_desc_get_tx_status,
 	.rx_status = enh_desc_get_rx_status,
 	.get_tx_len = enh_desc_get_tx_len,