bonding: Re-enable netpoll over bonding

With the inclusion of previous fixup patches, netpoll over bonding apears to
work reliably with failover conditions.  This reverts Gospos previous commit
c22d7ac8

, and allows access again to the netpoll
functionality in the bonding driver.

Signed-off-by: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>