idpf: disable local BH when scheduling napi for marker packets

Fix softirq's not being handled during napi_schedule() call when
receiving marker packets for queue disable by disabling local bottom
half.

The issue can be seen on ifdown:
NOHZ tick-stop error: Non-RCU local softirq work is pending, handler #08!!!

Using ftrace to catch the failing scenario:
ifconfig   [003] d.... 22739.830624: softirq_raise: vec=3 [action=NET_RX]
<idle>-0   [003] ..s.. 22739.831357: softirq_entry: vec=3 [action=NET_RX]

No interrupt and CPU is idle.

After the patch when disabling local BH before calling napi_schedule:
ifconfig   [003] d.... 22993.928336: softirq_raise: vec=3 [action=NET_RX]
ifconfig   [003] ..s1. 22993.928337: softirq_entry: vec=3 [action=NET_RX]

Fixes: c2d548ca ("idpf: add TX splitq napi poll support")
Reviewed-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Reviewed-by: Przemek Kitszel <przemyslaw.kitszel@intel.com>
Signed-off-by: Emil Tantilov <emil.s.tantilov@intel.com>
Signed-off-by: Alan Brady <alan.brady@intel.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Tested-by: Krishneil Singh <krishneil.k.singh@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>

drivers/net/ethernet/intel/idpf/idpf_virtchnl.c

@@ -2087,8 +2087,10 @@ int idpf_send_disable_queues_msg(struct idpf_vport *vport)
 		set_bit(__IDPF_Q_POLL_MODE, vport->txqs[i]->flags);
 
 	/* schedule the napi to receive all the marker packets */
+	local_bh_disable();
 	for (i = 0; i < vport->num_q_vectors; i++)
 		napi_schedule(&vport->q_vectors[i].napi);
+	local_bh_enable();
 
 	return idpf_wait_for_marker_event(vport);
 }