ixgbevf: Fix handling of NAPI budget when multiple queues are enabled per vector

BugLink: http://bugs.launchpad.net/bugs/1536473

This is the same patch as for ixgbe but applied differently according to
busy polling.  See commit 5d6002b7 ("ixgbe: Fix handling of NAPI
budget when multiple queues are enabled per vector")
Signed-off-by: William Dauchy <william@gandi.net>
Tested-by: Phil Schmitt <phillip.j.schmitt@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
(cherry picked from commit d0f71aff)
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>

drivers/net/ethernet/intel/ixgbevf/ixgbevf_main.c

@@ -1016,6 +1016,8 @@ static int ixgbevf_poll(struct napi_struct *napi, int budget)
 	ixgbevf_for_each_ring(ring, q_vector->tx)
 		clean_complete &= ixgbevf_clean_tx_irq(q_vector, ring);
 
+	if (budget <= 0)
+		return budget;
 #ifdef CONFIG_NET_RX_BUSY_POLL
 	if (!ixgbevf_qv_lock_napi(q_vector))
 		return budget;