staging: r8188eu: replace custom macros with is_broadcast_ether_addr

Replace usage of custom macros with is_broadcast_ether_addr. All buffers
are properly aligned. Remove the now unsued macros MacAddr_isBcst and
IS_MAC_ADDRESS_BROADCAST.

Signed-off-by: Michael Straube <straube.linux@gmail.com>
Acked-by: Larry Finger <Larry.Finger@lwfinger.net>
Link: https://lore.kernel.org/r/20210805205010.31192-1-straube.linux@gmail.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>