stmmac: dwmac-loongson: change loongson_dwmac_driver from global to static

Smatch reports this issue
dwmac-loongson.c:208:19: warning: symbol
  'loongson_dwmac_driver' was not declared.
  Should it be static?

loongson_dwmac_driver is only used in dwmac-loongson.c.
File scope variables used only in one file should
be static. Change loongson_dwmac_driver's
storage-class-specifier from global to static.
Signed-off-by: Tom Rix <trix@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/stmicro/stmmac/dwmac-loongson.c

@@ -205,7 +205,7 @@ static const struct pci_device_id loongson_dwmac_id_table[] = {
 };
 MODULE_DEVICE_TABLE(pci, loongson_dwmac_id_table);
 
-struct pci_driver loongson_dwmac_driver = {
+static struct pci_driver loongson_dwmac_driver = {
 	.name = "dwmac-loongson-pci",
 	.id_table = loongson_dwmac_id_table,
 	.probe = loongson_dwmac_probe,