dt-bindings: media: nxp,imx8mq-vpu: Update the bindings for G2 support

Introducing the G2 hevc video decoder requires modifications of the bindings to allow
one node per VPU.

VPUs share one hardware control block which is provided as a phandle on
a syscon.
Each node has now one reg and one interrupt.
Add a compatible for G2 hardware block: nxp,imx8mq-vpu-g2.

To be compatible with older DT the driver is still capable to use the 'ctrl'
reg-name even if it is deprecated now.

Signed-off-by: Benjamin Gaignard <benjamin.gaignard@collabora.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Philipp Zabel <p.zabel@pengutronix.de>