xen/events: remove some info_for_irq() calls in pirq handling

Instead of the IRQ number user the struct irq_info pointer as parameter
in the internal pirq related functions. This allows to drop some calls
of info_for_irq().

Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
Signed-off-by: Juergen Gross <jgross@suse.com>