net: apple: mace: Fix build since dev_addr constification

net: apple: mace: Fix build since dev_addr constification

Since commit adeef3e32146 ("net: constify netdev->dev_addr") the mace
driver no longer builds with various errors (pmac32_defconfig):

  linux/drivers/net/ethernet/apple/mace.c: In function ‘mace_probe’:
  linux/drivers/net/ethernet/apple/mace.c:170:20: error: assignment of read-only location ‘*(dev->dev_addr + (sizetype)j)’
    170 |   dev->dev_addr[j] = rev ? bitrev8(addr[j]): addr[j];
        |                    ^
  linux/drivers/net/ethernet/apple/mace.c: In function ‘mace_reset’:
  linux/drivers/net/ethernet/apple/mace.c:349:32: warning: passing argument 2 of ‘__mace_set_address’ discards ‘const’ qualifier from pointer target type
    349 |     __mace_set_address(dev, dev->dev_addr);
        |                             ~~~^~~~~~~~~~
  linux/drivers/net/ethernet/apple/mace.c:93:62: note: expected ‘void *’ but argument is of type ‘const unsigned char *’
     93 | static void __mace_set_address(struct net_device *dev, void *addr);
        |                                                        ~~~~~~^~~~
  linux/drivers/net/ethernet/apple/mace.c: In function ‘__mace_set_address’:
  linux/drivers/net/ethernet/apple/mace.c:388:36: error: assignment of read-only location ‘*(dev->dev_addr + (sizetype)i)’
    388 |  out_8(&mb->padr, dev->dev_addr[i] = p[i]);
        |                                    ^

Fix it by making the modifications to a local macaddr variable and then
passing that to eth_hw_addr_set(), as well as adding some missing const
qualifiers.

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>