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>