irqchip: Move IRQCHIP_DECLARE macro to include/linux/irqchip.h

irqchip: Move IRQCHIP_DECLARE macro to include/linux/irqchip.h

At the moment the IRQCHIP_DECLARE macro is only declared locally in
drivers/irqchip/irqchip.h. It prevents from using it directly in arch/*
directories whenever irqchip drivers only exist there, which happens in a few
cases (e.g. arc, arm, microblaze and mips).

This patch makes the macro to be globally defined, i.e. in
include/linux/irqchip.h, and thus usable for arch-specific declarations of
irqchip drivers. In this way, it is very similar to what clocksource does (ie
CLOCKSOURCE_OF_DECLARE is defined in include/linux/clocksource.h).

For now, this patch only moves the declaration of the macro
IRQCHIP_DECLARE to the global header 'include/linux/irqchip.h' and make
'drivers/irqchip/irqchip.h' include 'include/linux/irqchip.h'. Later, other
patches will get rid of 'drivers/irqchip/irqchip.h' and modify all the impacted
irqchip drivers.

Signed-off-by: Joel Porquet <joel@porquet.org>
Cc: Jason Cooper <jason@lakedaemon.net>
Link: http://lkml.kernel.org/r/1435865565-14114-1-git-send-email-joel@porquet.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>