dt-bindings: interrupt-controller: via,vt8500-intc: Convert to YAML

dt-bindings: interrupt-controller: via,vt8500-intc: Convert to YAML

Rewrite the textual description for the VIA/WonderMedia interrupt
controller as YAML schema.

The original textual version did not contain information about the
usage of 'interrupts' to describe the connection of a chained
controller to its parent, add it here. A chained controller can
trigger up to 8 different interrupts (IRQ0~7) on its parent.

Signed-off-by: Alexey Charkov <alchark@gmail.com>
Link: https://lore.kernel.org/r/20250418-via_intc_binding-v2-1-b649ce737f71@gmail.com
Signed-off-by: Rob Herring (Arm) <robh@kernel.org>