Existing code for drivers/net/wan/z8530 is riddled with self-deadlocks
and irq flag confusion.  For example:
	z8530_init -> do_z8530_init -> write_zsreg
self deadlocks on the channel lock.

Several places acquire both the channel and dma lock and then
reuse the same irq flags variable - ouch.

This code at least, correctly probes (for no device case) on SMP.
Other paths verified by inspection.