ssb: fix unaligned access to mac address

The mac address should be aligned to u16 to prevent an unaligned access
in drivers/ssb/pci.c where it is casted to __be16.

Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>
Signed-off-by: John W. Linville <linville@tuxdriver.com>