arm64: dts: meson-gx: Add canvas provider node to the vpu

Allows the vpu driver to optionally use a canvas provider node.

Signed-off-by: Maxime Jourdan <mjourdan@baylibre.com>
Acked-by: Neil Armstrong <narmstrong@baylibre.com>
Signed-off-by: Kevin Hilman <khilman@baylibre.com>