net: sunbmac: Replace in_interrupt() usage

bigmac_init_rings() has an argument signaling if it is called from the
interrupt handler. This is used to decide between GFP_KERNEL and GFP_ATOMIC
for memory allocations.

But it also checks in_interrupt() to handle invocations which come from the
timer callback bigmac_timer() via bigmac_hw_init(), which is invoked with
'in_irq = 0'. While the timer callback is clearly not in hard interrupt
context it is still not sleepable context.

Rename the argument to `non_blocking' and set it to true if invoked from
the timer callback or the interrupt handler which allows to remove the
in_interrupt() check and makes the code consistent.

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>