forcedeth: fix unilateral interrupt disabling in netpoll path

Forcedeth currently uses disable_irq_lockdep and enable_irq_lockdep, which in
some configurations simply calls local_irq_disable.  This causes errant warnings
in the netpoll path as in netpoll_send_skb_on_dev, where we disable irqs using
local_irq_save, leading to the following warning:

WARNING: at net/core/netpoll.c:352 netpoll_send_skb_on_dev+0x243/0x250() (Not
tainted)
Hardware name:
netpoll_send_skb_on_dev(): eth0 enabled interrupts in poll
(nv_start_xmit_optimized+0x0/0x860 [forcedeth])
Modules linked in: netconsole(+) configfs ipv6 iptable_filter ip_tables ppdev
parport_pc parport sg microcode serio_raw edac_core edac_mce_amd k8temp
snd_hda_codec_realtek snd_hda_codec_generic forcedeth snd_hda_intel
snd_hda_codec snd_hwdep snd_seq snd_seq_device snd_pcm snd_timer snd soundcore
snd_page_alloc i2c_nforce2 i2c_core shpchp ext4 jbd2 mbcache sr_mod cdrom sd_mod
crc_t10dif pata_amd ata_generic pata_acpi sata_nv dm_mirror dm_region_hash
dm_log dm_mod [last unloaded: scsi_wait_scan]
Pid: 1940, comm: modprobe Not tainted 2.6.32-573.7.1.el6.x86_64.debug #1
Call Trace:
 [<ffffffff8107bbc1>] ? warn_slowpath_common+0x91/0xe0
 [<ffffffff8107bcc6>] ? warn_slowpath_fmt+0x46/0x60
 [<ffffffffa00fe5b0>] ? nv_start_xmit_optimized+0x0/0x860 [forcedeth]
 [<ffffffff814b3593>] ? netpoll_send_skb_on_dev+0x243/0x250
 [<ffffffff814b37c9>] ? netpoll_send_udp+0x229/0x270
 [<ffffffffa02e3299>] ? write_msg+0x39/0x110 [netconsole]
 [<ffffffffa02e331b>] ? write_msg+0xbb/0x110 [netconsole]
 [<ffffffff8107bd55>] ? __call_console_drivers+0x75/0x90
 [<ffffffff8107bdba>] ? _call_console_drivers+0x4a/0x80
 [<ffffffff8107c445>] ? release_console_sem+0xe5/0x250
 [<ffffffff8107d200>] ? register_console+0x190/0x3e0
 [<ffffffffa02e71a6>] ? init_netconsole+0x1a6/0x216 [netconsole]
 [<ffffffffa02e7000>] ? init_netconsole+0x0/0x216 [netconsole]
 [<ffffffff810020d0>] ? do_one_initcall+0xc0/0x280
 [<ffffffff810d4933>] ? sys_init_module+0xe3/0x260
 [<ffffffff8100b0d2>] ? system_call_fastpath+0x16/0x1b
---[ end trace f349c7af88e6a6d5 ]---
console [netcon0] enabled
netconsole: network logging started

Fix it by modifying the forcedeth code to use
disable_irq_nosync_lockdep_irqsavedisable_irq_nosync_lockdep_irqsave instead,
which saves and restores irq state properly.  This also saves us a little code
in the process

Tested by the reporter, with successful restuls

Patch applies to the head of the net tree

Signed-off-by: Neil Horman <nhorman@tuxdriver.com>
CC: "David S. Miller" <davem@davemloft.net>
Reported-by: Vasily Averin <vvs@sw.ru>
Signed-off-by: David S. Miller <davem@davemloft.net>