b44: the poll handler b44_poll must not enable IRQ unconditionally

net/core/netpoll.c::netpoll_send_skb() calls the poll handler when
it is available. As netconsole can be used from almost any context,
IRQ must not be enabled blindly in the NAPI handler of the driver
which supports netpoll.

Call trace:
netpoll_send_skb()
{
local_irq_save(flags)
  -> netpoll_poll()
    -> poll_napi()
      -> poll_one_napi()
        -> napi->poll()
            -> b44_poll()
local_irq_restore(flags)
}

Signed-off-by: Dongdong Deng <dongdong.deng@windriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>