net: apple: bmac: Fix build since dev_addr constification

Since commit adeef3e3 ("net: constify netdev->dev_addr") the bmac
driver no longer builds with the following errors (pmac32_defconfig):

  linux/drivers/net/ethernet/apple/bmac.c: In function ‘bmac_probe’:
  linux/drivers/net/ethernet/apple/bmac.c:1287:20: error: assignment of read-only location ‘*(dev->dev_addr + (sizetype)j)’
   1287 |   dev->dev_addr[j] = rev ? bitrev8(addr[j]): addr[j];
        |                    ^

Fix it by making the modifications to a local macaddr variable and then
passing that to eth_hw_addr_set().

We don't use the existing addr variable because the bitrev8() would
mutate it, but it is already used unreversed later in the function.
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Reviewed-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/apple/bmac.c

@@ -1237,6 +1237,7 @@ static int bmac_probe(struct macio_dev *mdev, const struct of_device_id *match)
 	struct bmac_data *bp;
 	const unsigned char *prop_addr;
 	unsigned char addr[6];
+	u8 macaddr[6];
 	struct net_device *dev;
 	int is_bmac_plus = ((int)match->data) != 0;
 
@@ -1284,7 +1285,9 @@ static int bmac_probe(struct macio_dev *mdev, const struct of_device_id *match)
 
 	rev = addr[0] == 0 && addr[1] == 0xA0;
 	for (j = 0; j < 6; ++j)
-		dev->dev_addr[j] = rev ? bitrev8(addr[j]): addr[j];
+		macaddr[j] = rev ? bitrev8(addr[j]): addr[j];
+
+	eth_hw_addr_set(dev, macaddr);
 
 	/* Enable chip without interrupts for now */
 	bmac_enable_and_reset_chip(dev);