usb: dwc2: Deprecate g-use-dma binding

This is not needed as the gadget now fully supports DMA and it can
autodetect it. This was initially added because gadget DMA mode was only
partially implemented so could not be automatically enabled.

Signed-off-by: John Youn <johnyoun@synopsys.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

Documentation/devicetree/bindings/usb/dwc2.txt

@@ -25,11 +25,13 @@ Optional properties:
 Refer to phy/phy-bindings.txt for generic phy consumer properties
 - dr_mode: shall be one of "host", "peripheral" and "otg"
   Refer to usb/generic.txt
-- g-use-dma: enable dma usage in gadget driver.
 - g-rx-fifo-size: size of rx fifo size in gadget mode.
 - g-np-tx-fifo-size: size of non-periodic tx fifo size in gadget mode.
 - g-tx-fifo-size: size of periodic tx fifo per endpoint (except ep0) in gadget mode.
 
+Deprecated properties:
+- g-use-dma: gadget DMA mode is automatically detected
+
 Example:
 
         usb@101c0000 {