CS89x0: Finish transition to CS89x0_NONISA_IRQ

CS89x0_NONISA_IRQ is selected by all those non-ISA boards which use
CS89x0. This patch only cleans the last bits left after its introduction.

Signed-off-by: Domenico Andreoli <cavokz@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>