Cleanup jmr3927, tx4927 and tx4938 irq codes, using common IRQ_CPU,
I8259 and IRQ_TXX9 irq routines.
Signed-off-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>