bcm63xx_enet: change the driver variables to static

bcm63xx_enetsw_driver and bcm63xx_enet_driver are only used in
bcm63xx_enet.c now, change them to static.
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Link: https://lore.kernel.org/r/20220707135801.1483941-1-yangyingliang@huawei.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/broadcom/bcm63xx_enet.c

@@ -1935,7 +1935,7 @@ static int bcm_enet_remove(struct platform_device *pdev)
 	return 0;
 }
 
-struct platform_driver bcm63xx_enet_driver = {
+static struct platform_driver bcm63xx_enet_driver = {
 	.probe	= bcm_enet_probe,
 	.remove	= bcm_enet_remove,
 	.driver	= {
@@ -2756,7 +2756,7 @@ static int bcm_enetsw_remove(struct platform_device *pdev)
 	return 0;
 }
 
-struct platform_driver bcm63xx_enetsw_driver = {
+static struct platform_driver bcm63xx_enetsw_driver = {
 	.probe	= bcm_enetsw_probe,
 	.remove	= bcm_enetsw_remove,
 	.driver	= {