[MIPS] Alchemy: Get rid of au1xxx_irq_map_t.

arch/mips/au1000/common/au1xxx_irqmap.c

arch/mips/au1000/common/irq.c

arch/mips/au1000/db1x00/irqmap.c

arch/mips/au1000/mtx-1/irqmap.c

arch/mips/au1000/pb1000/irqmap.c

arch/mips/au1000/pb1100/irqmap.c

arch/mips/au1000/pb1200/irqmap.c

arch/mips/au1000/pb1500/irqmap.c

arch/mips/au1000/pb1550/irqmap.c

arch/mips/au1000/xxs1500/irqmap.c

include/asm-mips/mach-au1x00/au1000.h