dt-bindings: usb: typec: add bindings for stm32g0 controller

Add DT schema documentation for the STM32G0 Type-C PD (Power Delivery)
controller.
STM32G0 provides an integrated USB Type-C and power delivery interface.
It can be programmed with a firmware to handle UCSI protocol over I2C
interface. A GPIO is used as an interrupt line.
It may be used as a wakeup source, so use optional "wakeup-source" and
"power-domains" properties to support wakeup.
The firmware itself may be flashed or later updated (optional). Choice is
let to the application to allow firmware update. A default firmware could
be already programmed in production and be customized (to not allow it).
So the firmware-name is made optional to represent this option.

Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Fabrice Gasnier <fabrice.gasnier@foss.st.com>
Link: https://lore.kernel.org/r/20220713120842.560902-2-fabrice.gasnier@foss.st.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>