hv_netvsc: use netif_is_bond_master() instead of open code

Use netif_is_bond_master() function instead of open code, which is
((event_dev->priv_flags & IFF_BONDING) && (event_dev->flags & IFF_MASTER)).
This patch doesn't change logic.

Signed-off-by: Juhee Kang <claudiajkang@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>