genirq/irqdomain: Add map counter

Add a map counter instead of counting radix tree entries for
diagnosis. That also gives correct information for linear domains.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Marc Zyngier <marc.zyngier@arm.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Keith Busch <keith.busch@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Christoph Hellwig <hch@lst.de>
Link: http://lkml.kernel.org/r/20170619235444.459397746@linutronix.de

include/linux/irqdomain.h

@@ -130,6 +130,7 @@ struct irq_domain_chip_generic;
  * @host_data: private data pointer for use by owner.  Not touched by irq_domain
  *             core code.
  * @flags: host per irq_domain flags
+ * @mapcount: The number of mapped interrupts
  *
  * Optional elements
  * @of_node: Pointer to device tree nodes associated with the irq_domain. Used
@@ -152,6 +153,7 @@ struct irq_domain {
 	const struct irq_domain_ops *ops;
 	void *host_data;
 	unsigned int flags;
+	unsigned int mapcount;
 
 	/* Optional data */
 	struct fwnode_handle *fwnode;