This patch adds support for STUSB1600 USB Type-C port controller, used on
I2C4 on stm32mp15xx-dkx.
The default configuration on this board, on Type-C connector, is:
- Dual Power Role (DRP), so set power-role to "dual";
- Vbus limited to 500mA, so set typec-power-opmode to "default" (it means
  500mA in USB 2.0).
typec-power-opmode is used to reconfigure the STUSB1600 advertising of
current capability when its NVM is not in line with the board layout.
On stm32mp15xx-dkx, Vbus power source of STUSB1600 is 5V_VIN. So power
operation mode depends on the power supply used. To avoid any power
issues, it is better to limit Vbus to 500mA on this board.
ALERT# is the interrupt pin of STUSB1600. It needs an external pull-up, and
signal is active low.

USB OTG controller ID and Vbus signals are not connected on stm32mp15xx-dkx
boards, so disconnection are not detected.
Without DWC2 usb-role-switch:
- if you unplug the USB cable from the Type-C port, you have to manually
disconnect the USB gadget:
echo disconnect > /sys/devices/platform/soc/49000000.usb-otg/udc/49000000.usb-otg/soft_connect
- Then you can plug the USB cable again in the Type-C port, and manually
reconnect the USB gadget:
echo connect > /sys/devices/platform/soc/49000000.usb-otg/udc/49000000.usb-otg/soft_connect
With DWC2 usb-role-switch, USB gadget is dynamically disconnected or connected.
Signed-off-by: Amelie Delaunay <amelie.delaunay@st.com>
Signed-off-by: Alexandre Torgue <alexandre.torgue@st.com>