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/dwmac100.h b/drivers/net/stmmac/dwmac100.h
index 97956cbf1..7c6d857 100644
--- a/drivers/net/stmmac/dwmac100.h
+++ b/drivers/net/stmmac/dwmac100.h
@@ -118,4 +118,4 @@
 #define DMA_MISSED_FRAME_OVE_M	0x00010000	/* Missed Frame Overflow */
 #define DMA_MISSED_FRAME_M_CNTR	0x0000ffff	/* Missed Frame Couinter */
 
-extern struct stmmac_dma_ops dwmac100_dma_ops;
+extern const struct stmmac_dma_ops dwmac100_dma_ops;