Fix issue with out of tree/dir building

[tingleby]

When building errors occur with the jz4740/irq.h, with a specified output directory (e.g make O=output) would fail with the following:

  CC      arch/mips/jz4740/time.o
In file included from ../arch/mips/include/asm/irq.h:18:0,
                 from ../include/linux/irq.h:24,
                 from ../include/asm-generic/hardirq.h:12,
                 from ../arch/mips/include/asm/hardirq.h:16,
                 from ../include/linux/hardirq.h:8,
                 from ../include/linux/interrupt.h:12,
                 from ../arch/mips/jz4740/time.c:18:
../arch/mips/jz4740/irq.h:20:39: error: 'struct irq_data' declared inside parameter list [-Werror]
 extern void jz4740_irq_suspend(struct irq_data *data);
                                       ^
../arch/mips/jz4740/irq.h:20:39: error: its scope is only this definition or declaration, which is probably not what you want [-Werror]
../arch/mips/jz4740/irq.h:21:38: error: 'struct irq_data' declared inside parameter list [-Werror]
 extern void jz4740_irq_resume(struct irq_data *data);
                                      ^
In file included from ../include/linux/irq.h:380:0,
                 from ../include/asm-generic/hardirq.h:12,
                 from ../arch/mips/include/asm/hardirq.h:16,
                 from ../include/linux/hardirq.h:8,
                 from ../include/linux/interrupt.h:12,
                 from ../arch/mips/jz4740/time.c:18:
../include/linux/irqdesc.h:92:33: error: 'NR_IRQS' undeclared here (not in a function)
 extern struct irq_desc irq_desc[NR_IRQS];

Patch moves the irq.h header to a include directory and is then specifically included where used.

[ZubairLK]

Thank-you for the pull request.

@paulburton @aejsmith is it ok way to move the header around?

[pcercuei]

The problem here, is that arch/mips/jz4740/irq.h is a "reserved" name; if it exists it will be included by arch/mips/include/asm/irq.h instead of the correct header.

Moving the file is the right solution, but it should be moved to e.g. arch/mips/jz4740/irq-jz4740.h and not inside include/.

[tingleby]

Yeah I wasn't really sure what to-do with the header, so i copied the way another irqchip driver handles it.
I've updated the patch.