genirq: Add state field to irq_data

Some chip implementations need to access certain status flags. With
sparse irqs that requires a lookup of the irq descriptor. Add a state
field which contains such flags.

Name it in a way which will make coders happy to access it with the
proper accessor functions. And it's easy to grep for.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

include/linux/irqdesc.h

@@ -48,6 +48,7 @@ struct irq_desc {
 		struct {
 			unsigned int		irq;
 			unsigned int		node;
+			unsigned int		pad_do_not_even_think_about_it;
 			struct irq_chip		*chip;
 			void			*handler_data;
 			void			*chip_data;