driver: macvlan: Replace integer number with bool value

The return value of function macvlan_addr_busy is used as bool value,
so use bool value instead of integer number "1" and "0".

Signed-off-by: Gao Feng <gfree.wind@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
1 file changed