netxen_nic: use spin_[un]lock_bh around tx_clean_lock (2)

This patch should have been part of the previous patch having the
same summary. See  http://marc.info/?l=linux-kernel&m=143039470103795&w=2
Unfortunately, I didn't check to see where else this lock was used before
submitting that patch. This should take care of it for netxen_nic, as I
did a thorough search this time.

To recap from the original patch; although testing this driver with
DEBUG_LOCKDEP and DEBUG_SPINLOCK enabled did not produce any traces,
it would be more prudent in the case of tx_clean_lock to use _bh
versions of spin_[un]lock, since this lock is manipulated in both
the process and softirq contexts.

This patch was tested for functionality and regressions with netperf
and DEBUG_LOCKDEP and DEBUG_SPINLOCK enabled.

Signed-off-by: Tony Camuso <tcamuso@redhat.com>
Acked-By: Neil Horman <nhorman@tuxdriver.com>
Acked-By: Manish Chopra <manish.chopra@qlogic.com>
Signed-off-by: David S. Miller <davem@davemloft.net>