irqdesc: Add domain handler for NMIs

irqdesc: Add domain handler for NMIs

NMI handling code should be executed between calls to nmi_enter and
nmi_exit.

Add a separate domain handler to properly setup NMI context when handling
an interrupt requested as NMI.

Signed-off-by: Julien Thierry <julien.thierry@arm.com>
Acked-by: Marc Zyngier <marc.zyngier@arm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>