MLK-23412-10 usb: dwc3: imx8mp: update binding doc to add one clock

For dwc3-imx8mp, the clock for its power domain hsiomix has
to be handled by user, so add the hsio root clock to dwc3 imx8mp
binding doc.

Reviewed-by: Peter Chen <peter.chen@nxp.com>
Signed-off-by: Li Jun <jun.li@nxp.com>

Documentation/devicetree/bindings/usb/dwc3-imx8mp.txt

@@ -10,8 +10,9 @@ Required properties:
  - clocks	: A list of phandle + clock-specifier pairs for the
 		  clocks listed in clock-names
  - clock-names	: Should contain the following:
+		  "hsio" hsio root clock
 		  "bus" System bus AXI clock
-		  "sleep" Sleep clock, used for wakeup.
+		  "suspend" Suspend clock, used for wakeup.
  - interrupts	: specifies interrupt from controller wrapper used
 		  to wakeup from low power/susepnd state.