dt-bindings: i2c: brcmstb: Add BCM2711 BSC/AUTO-I2C binding

The HDMI blocks in the BCM2771 have an i2c controller to retrieve the
EDID. This block is split into two parts, the BSC and the AUTO_I2C,
lying in two separate register areas.

The AUTO_I2C block has a mailbox-like interface and will take away the
BSC control from the CPU if enabled. However, the BSC is the actually
the same controller than the one supported by the brcmstb driver, and
the AUTO_I2C doesn't really bring any immediate benefit.

We can model it in the DT as a single device with two register range,
which will allow us to use or or the other in the driver without
changing anything in the DT.

Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Acked-by: Florian Fainelli <f.fainelli@gmail.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>