bridge: Use helpers to handle MAC address

Use
	%pM to print MAC
	mac_pton() to convert it from ASCII to binary format, and
	ether_addr_copy() to copy.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
Signed-off-by: David S. Miller <davem@davemloft.net>