dt-bindings: usb: mtu3: remove dummy clocks and add optional ones

Remove dummy clocks for usb wakeup and add optional ones for
mcu_bus and dma_bus bus.
Signed-off-by: Chunfeng Yun <chunfeng.yun@mediatek.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

Documentation/devicetree/bindings/usb/mediatek,mtu3.txt

@@ -14,9 +14,9 @@ Required properties:
  - vusb33-supply : regulator of USB avdd3.3v
  - clocks : a list of phandle + clock-specifier pairs, one for each
 	entry in clock-names
- - clock-names : must contain "sys_ck" and "ref_ck" for clock of controller;
-	"wakeup_deb_p0" and "wakeup_deb_p1" are optional, they are
-	depends on "mediatek,enable-wakeup"
+ - clock-names : must contain "sys_ck" for clock of controller,
+	the following clocks are optional:
+	"ref_ck", "mcu_ck" and "dam_ck";
  - phys : a list of phandle + phy specifier pairs
  - dr_mode : should be one of "host", "peripheral" or "otg",
 	refer to usb/generic.txt
@@ -65,9 +65,7 @@ ssusb: usb@11271000 {
 	clocks = <&topckgen CLK_TOP_USB30_SEL>, <&clk26m>,
 		 <&pericfg CLK_PERI_USB0>,
 		 <&pericfg CLK_PERI_USB1>;
-	clock-names = "sys_ck", "ref_ck",
-		      "wakeup_deb_p0",
-		      "wakeup_deb_p1";
+	clock-names = "sys_ck", "ref_ck";
 	vusb33-supply = <&mt6397_vusb_reg>;
 	vbus-supply = <&usb_p0_vbus>;
 	extcon = <&extcon_usb>;