dt-bindings: ingenic,i2c: Rework interrupts in example

In order to determine the number of interrupt cells in examples, the
examples will require all 'interrupts' properties to use the same number
of cells or have explicit interrupt provider node(s). As the former is
simpler, update the Ingenic example to use 2 interrupt cells everywhere.

Signed-off-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20220119174349.3809513-1-robh@kernel.org