net: stmmac: make const array route_possibilities static

Don't populate array route_possibilities on the stack but make it
static const.  Makes the object code a little smaller by 85 bytes:

Before:
   text	   data	    bss	    dec	    hex	filename
   9901	   2448	      0	  12349	   303d	dwmac4_core.o

After:
   text	   data	    bss	    dec	    hex	filename
   9760	   2504	      0	  12264	   2fe8	dwmac4_core.o
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/stmicro/stmmac/dwmac4_core.c

@@ -117,7 +117,7 @@ static void dwmac4_tx_queue_routing(struct mac_device_info *hw,
 	void __iomem *ioaddr = hw->pcsr;
 	u32 value;
 
-	const struct stmmac_rx_routing route_possibilities[] = {
+	static const struct stmmac_rx_routing route_possibilities[] = {
 		{ GMAC_RXQCTRL_AVCPQ_MASK, GMAC_RXQCTRL_AVCPQ_SHIFT },
 		{ GMAC_RXQCTRL_PTPQ_MASK, GMAC_RXQCTRL_PTPQ_SHIFT },
 		{ GMAC_RXQCTRL_DCBCPQ_MASK, GMAC_RXQCTRL_DCBCPQ_SHIFT },