rtlwifi: Fix possible unaligned array in ether_addr_copy()

Two macros used to copy BSSID information use ether_addr_copy(), thus
the arrays must be 2-byte aligned. In one case, the array could become
unaligned if the struct containing it were changed. Use the __unaligned(2)
attribute to retain the necessary alignment. In addition, the magic number
used to specify the size of the array is replaced by ETH_ALEN.

Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Acked-by: David S. Miller <davem@davemloft.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>