genirq: Use the proper parameter name in kernel doc

The following warning is emitted for make xmldocs:

 Warning(.//kernel/irq/chip.c:1009): No description found for parameter 'vcpu_info'
 Warning(.//kernel/irq/chip.c:1009): Excess function parameter 'dest' description in 'irq_chip_set_vcpu_affinity_parent'


Signed-off-by: Masanari Iida <standby24x7@gmail.com>
Link: http://lkml.kernel.org/r/1438164576-5945-1-git-send-email-standby24x7@gmail.com


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