dt-bindings: usb: Document the STM32F7xx DWC2 USB OTG HS core binding

This patch adds binding documentation for DWC2 controller in HS mode found
on STMicroelectronics STM32F7xx SoC.
Signed-off-by: Amelie Delaunay <amelie.delaunay@st.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

Documentation/devicetree/bindings/usb/dwc2.txt

@@ -19,6 +19,8 @@ Required properties:
   configured in FS mode;
   - "st,stm32f4x9-hsotg": The DWC2 USB HS controller instance in STM32F4x9 SoCs
   configured in HS mode;
+  - "st,stm32f7xx-hsotg": The DWC2 USB HS controller instance in STM32F7xx SoCs
+    configured in HS mode;
 - reg : Should contain 1 register range (address and length)
 - interrupts : Should contain 1 interrupt
 - clocks: clock provider specifier