dts: Add 'AI Camera' support

The AI Camera combines an IMX500 and a RP2040 GPIO bridge on a single
module. The Raspberry Pi camera regulator is used for both IMX500 and
RP2040. SPI, clocks, and reset (required by IMX500) are provided by the
RP2040 GPIO bridge.

Signed-off-by: Richard Oliver <richard.oliver@raspberrypi.com>