pci: intr-remap: Free irte memory if SPARSE_IRQ=y

With SPARSE_IRQ=y the irte descriptors are dynamically allocated, but not
freed in free_irte().

That was ok as long as the sparse irq core was not freeing irq descriptors on
destroy_irq(). Now we leak the irte descriptor. Free it in free_irte().

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Ingo Molnar <mingo@elte.hu>
Acked-by: Suresh Siddha <suresh.b.siddha@intel.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Jesse Barnes <jbarnes@virtuousgeek.org>