dt-bindings: timer: arm,arch_timer: Add interrupt-names support

Not all platforms provide the same set of timers/interrupts, and Linux
only needs one (plus kvm/guest ones); some platforms are working around
this by using dummy fake interrupts. Implementing interrupt-names allows
the devicetree to specify an arbitrary set of available interrupts, so
the timer code can pick the right one.

This also adds the hyp-virt timer/interrupt, which was previously not
expressed in the fixed 4-interrupt form.

Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Tony Lindgren <tony@atomide.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Hector Martin <marcan@marcan.st>