net: sun3lance: Remove redundant checks in interrupt handler

lance_interrupt() contains two pointless checks:

 - A check whether the 'dev_id' argument is NULL. 'dev_id' is the pointer
   which was handed in to request_irq() and the interrupt handler will
   always be invoked with that pointer as 'dev_id' argument by the core
   code.

 - A check for interrupt reentrancy. The core code already guarantees
   non-reentrancy of interrupt handlers.

Remove these check.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: David S. Miller <davem@davemloft.net>