cxgb3: Fix lockdep problems with sge.reg_lock

cxgb3: Fix lockdep problems with sge.reg_lock

Using iWARP with a Chelsio T3 NIC generates the following lockdep warning:

    =================================
    [ INFO: inconsistent lock state ]
    2.6.25-rc6 #50
    ---------------------------------
    inconsistent {softirq-on-W} -> {in-softirq-W} usage.
    swapper/0 [HC0[0]:SC1[1]:HE0:SE0] takes:
     (&adap->sge.reg_lock){-+..}, at: [<ffffffff880e5ee2>] cxgb_offload_ctl+0x3af/0x507 [cxgb3]

The problem is that reg_lock is used with plain spin_lock() in
drivers/net/cxgb3/sge.c but is used with spin_lock_irqsave() in
drivers/net/cxgb3/cxgb3_offload.c.  This is technically a false
positive, since the uses in sge.c are only in the initialization and
cleanup paths and cannot overlap with any use in interrupt context.

The best fix is probably just to use spin_lock_irq() with reg_lock in
sge.c.  Even though it's not strictly required for correctness, it
avoids triggering lockdep and the extra overhead of disabling
interrupts is not important at all in the initialization and cleanup
slow paths.

Signed-off-by: Roland Dreier <rolandd@cisco.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>