cirrus/mac89x0: print MAC via printk format specifier

Print MAC/dev_addr via printk extended format specifier %pM instead
of custom code.

Use memcpy to set the address to dev->dev_addr in set_mac_address,
instead of mxing it up in a for loop with printing a debug msg.

Check also if the given address is valid.

Signed-off-by: Danny Kukawka <danny.kukawka@bisect.de>
Signed-off-by: David S. Miller <davem@davemloft.net>