ipv4: disable BH when changing ip local port range

This fixes the following lockdep warning:

 [ INFO: inconsistent lock state ]
 4.3.0-rc7+ #1197 Not tainted
 ---------------------------------
 inconsistent {IN-SOFTIRQ-R} -> {SOFTIRQ-ON-W} usage.
 sysctl/1019 [HC0[0]:SC0[0]:HE1:SE1] takes:
  (&(&net->ipv4.ip_local_ports.lock)->seqcount){+.+-..}, at: [<ffffffff81921de7>] ipv4_local_port_range+0xb4/0x12a
 {IN-SOFTIRQ-R} state was registered at:
   [<ffffffff810bd682>] __lock_acquire+0x2f6/0xdf0
   [<ffffffff810be6d5>] lock_acquire+0x11c/0x1a4
   [<ffffffff818e599c>] inet_get_local_port_range+0x4e/0xae
   [<ffffffff8166e8e3>] udp_flow_src_port.constprop.40+0x23/0x116
   [<ffffffff81671cb9>] vxlan_xmit_one+0x219/0xa6a
   [<ffffffff81672f75>] vxlan_xmit+0xa6b/0xaa5
   [<ffffffff817f2deb>] dev_hard_start_xmit+0x2ae/0x465
   [<ffffffff817f35ed>] __dev_queue_xmit+0x531/0x633
   [<ffffffff817f3702>] dev_queue_xmit_sk+0x13/0x15
   [<ffffffff818004a5>] neigh_resolve_output+0x12f/0x14d
   [<ffffffff81959cfa>] ip6_finish_output2+0x344/0x39f
   [<ffffffff8195bf58>] ip6_finish_output+0x88/0x8e
   [<ffffffff8195bfef>] ip6_output+0x91/0xe5
   [<ffffffff819792ae>] dst_output_sk+0x47/0x4c
   [<ffffffff81979392>] NF_HOOK_THRESH.constprop.30+0x38/0x82
   [<ffffffff8197981e>] mld_sendpack+0x189/0x266
   [<ffffffff8197b28b>] mld_ifc_timer_expire+0x1ef/0x223
   [<ffffffff810de581>] call_timer_fn+0xfb/0x28c
   [<ffffffff810ded1e>] run_timer_softirq+0x1c7/0x1f1

Fixes: b8f1a556 ("udp: Add function to make source port for UDP tunnels")
Cc: Tom Herbert <tom@herbertland.com>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>