genirq: Update irq stats from NMI handlers

The NMI handlers handle_percpu_devid_fasteoi_nmi() and handle_fasteoi_nmi()
do not update the interrupt counts. Due to that the NMI interrupt count
does not show up correctly in /proc/interrupts.

Add the statistics and treat the NMI handlers in the same way as per cpu
interrupts and prevent them from updating irq_desc::tot_count as this might
be corrupted due to concurrency.

[ tglx: Massaged changelog ]

Fixes: 2dcf1fbc ("genirq: Provide NMI handlers")
Signed-off-by: Shijith Thotton <sthotton@marvell.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/1562313336-11888-1-git-send-email-sthotton@marvell.com