media: dt-bindings: media: rkisp1: document different irq possibilities

Some variants have one irq signaling all of MI, MIPI and ISP events
while some rkisp1 variants use separate irqs for each.

Adapt the binding to handle both cases.

Signed-off-by: Heiko Stuebner <heiko.stuebner@theobroma-systems.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>