bnxt: use netif_is_rxfh_configured instead of open code

The open code which is dev->priv_flags & IFF_RXFH_CONFIGURED is defined as
a helper function on netdevice.h. So use netif_is_rxfh_configured()
function instead of open code. This patch doesn't change logic.

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