ethernet: constify references to netdev->dev_addr in drivers

This big patch sprinkles const on local variables and
function arguments which may refer to netdev->dev_addr.

Commit 406f42fa0d3c ("net-next: When a bond have a massive amount
of VLANs...") introduced a rbtree for faster Ethernet address look
up. To maintain netdev->dev_addr in this tree we need to make all
the writes to it got through appropriate helpers.

Some of the changes here are not strictly required - const
is sometimes cast off but pointer is not used for writing.
It seems like it's still better to add the const in case
the code changes later or relevant -W flags get enabled
for the build.

No functional changes.

Link: https://lore.kernel.org/r/20211014142432.449314-1-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
diff --git a/drivers/net/ethernet/ethoc.c b/drivers/net/ethernet/ethoc.c
index cd3a3b8..ed2ef16 100644
--- a/drivers/net/ethernet/ethoc.c
+++ b/drivers/net/ethernet/ethoc.c
@@ -802,8 +802,8 @@ static int ethoc_ioctl(struct net_device *dev, struct ifreq *ifr, int cmd)
 
 static void ethoc_do_set_mac_address(struct net_device *dev)
 {
+	const unsigned char *mac = dev->dev_addr;
 	struct ethoc *priv = netdev_priv(dev);
-	unsigned char *mac = dev->dev_addr;
 
 	ethoc_write(priv, MAC_ADDR0, (mac[2] << 24) | (mac[3] << 16) |
 				     (mac[4] <<  8) | (mac[5] <<  0));