[TG3]: Fix irq_sync race condition.

[TG3]: Fix irq_sync race condition.

Gagan Arneja <gaagaan@gmail.com> pointed out that tg3_reset_task()
could potentially race with another thread calling tg3_full_lock()
such as the ethtool_set_xxx() functions.  This may trigger the
BUG_ON() in tg3_irq_quiesce() or cause the irq_sync flag to be out-
of-sync.

I think the easiest way to fix this is to get the tp->lock first
before setting the irq_sync flag.  This is safe to do because the
tp->lock is never grabbed by the irq handler.  This change will
guarantee that the irq_sync flag updates will be serialized.  We also
have to change one spot to call tg3_netif_start() (which clears the
irq_sync flag) before releasing the tp->lock.

Signed-off-by: Michael Chan <mchan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>