arm_pmu: arm64: Use NMIs for PMU

Add required PMU interrupt operations for NMIs. Request interrupt lines as
NMIs when possible, otherwise fall back to normal interrupts.

NMIs are only supported on the arm64 architecture with a GICv3 irqchip.

Signed-off-by: Julien Thierry <julien.thierry@arm.com>
[Clarified that NMIs only work on arm64 + GICv3]
Signed-off-by: Alexandru Elisei <alexandru.elisei@arm.com>
Tested-by: Shijith Thotton <sthotton@marvell.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>