smc91c92_cs: spin_unlock_irqrestore before calling smc_interrupt()

smc91c92_cs:
  * spin_unlock_irqrestore before calling smc_interrupt() in media_check()
     to avoid lockup.
  * use spin_lock_irqsave for ethtool function.

Signed-off-by: Ken Kawasaki <ken_kawasaki@spring.nifty.jp>
Signed-off-by: David S. Miller <davem@davemloft.net>