smc91c92_cs:
  Fix the problem that lan & modem does not work simultaneously
  in the Megahertz multi-function card.
  We need to write MEGAHERTZ_ISR to retrigger interrupt.
Signed-off-by: NKen Kawasaki <ken_kawasaki@spring.nifty.jp>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>