bonding: use return instead of goto

Replace 'goto' with 'return' to remove unnecessary check at label:
err_undo_flags.

The reason is that 'err_undo_flags' do two things for the first slave device:
1.revert bond mac address if it is set by the slave device.
2.revert bond device type if it's not ARPHRD_ETHER.

It's not necessary for the following three places, they changed neither bond
mac address nor type. It's straightforward to return directly.

Signed-off-by: Zhang Shengju <zhangshengju@cmss.chinamobile.com>
Signed-off-by: David S. Miller <davem@davemloft.net>