The gfp parameter was added in:
commit 47be03a2
Author: Amerigo Wang <amwang@redhat.com>
Date:   Fri Aug 10 01:24:37 2012 +0000

    netpoll: use GFP_ATOMIC in slave_enable_netpoll() and __netpoll_setup()

    slave_enable_netpoll() and __netpoll_setup() may be called
    with read_lock() held, so should use GFP_ATOMIC to allocate
    memory. Eric suggested to pass gfp flags to __netpoll_setup().

    Cc: Eric Dumazet <eric.dumazet@gmail.com>
    Cc: "David S. Miller" <davem@davemloft.net>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Cong Wang <amwang@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

The reason for the gfp parameter was removed in:
commit c4cdef9b
Author: dingtianhong <dingtianhong@huawei.com>
Date:   Tue Jul 23 15:25:27 2013 +0800

    bonding: don't call slave_xxx_netpoll under spinlocks

    The slave_xxx_netpoll will call synchronize_rcu_bh(),
    so the function may schedule and sleep, it should't be
    called under spinlocks.

    bond_netpoll_setup() and bond_netpoll_cleanup() are always
    protected by rtnl lock, it is no need to take the read lock,
    as the slave list couldn't be changed outside rtnl lock.
Signed-off-by: Ding Tianhong <dingtianhong@huawei.com>
    Cc: Jay Vosburgh <fubar@us.ibm.com>
    Cc: Andy Gospodarek <andy@greyhouse.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

Nothing else that calls __netpoll_setup or ndo_netpoll_setup
requires a gfp paramter, so remove the gfp parameter from both
of these functions making the code clearer.
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: David S. Miller <davem@davemloft.net>