genirq/generic_chip: Verify irqs_per_chip <= 32

genirq/generic_chip: Verify irqs_per_chip <= 32

Most (if not all) code here implicitly assumes that the maximum number of
IRQs per chip will be 32, and thus uses 'u32' or 'unsigned long' for many
tasks (for example "struct irq_data" declares its 'mask' field as 'u32',
and "struct irq_chip_generic" declares its 'installed' field as 'unsigned
long')

However, there is no check to verify that irqs_per_chip is <= 32.  Hence,
calling irq_alloc_domain_generic_chips() with a bigger value will result in
unexpected results.

Provide a wrapper with a MAYBE_BUILD_BUG_ON(nrirqs >= 32) to catch such
cases.

[ tglx: Reduced changelog to the essential information ]

Signed-off-by: Sebastian Frias <sf84@laposte.net>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Cc: Mason <slash.tmp@free.fr>
Cc: Jason Cooper <jason@lakedaemon.net>
Link: http://lkml.kernel.org/r/57B31D94.5040701@laposte.net
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>