staging: rtl8723au: Fix alignment of mac_addr for ether_addr_copy() usage

Make sure struct eeprom_priv->mac_addr is 2 byte aligned to work with
ether_addr_copy()

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Jes Sorensen <Jes.Sorensen@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>