ethernet: Use bool function returns of true/false instead of 1/0

Use bool constants as the return values instead of 1 and 0.

Signed-off-by: Joe Perches <joe@perches.com>
Acked-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>