dt-bindings: usb: Document qcom,qmp-phy-override-seq

Document the newly introduced optional property that can be used
to override the QMP phy sequence. This property contains array of
reg-offset, value pair.

Change-Id: I7b1a934fb6c083a59c28e881b08dfa9fe653eff8

bindings/usb/qcom,msm-phy.txt

@@ -125,6 +125,7 @@ Optional properties:
             of lanes used in case of USB+DP concurrent mode to driver.
  - usb3_dp_phy_gdsc-supply: phandle to GDSC regulator device tree node related
    to USB QMP DP PHY.
+ - qcom,qmp-phy-override-seq : QMP PHY override sequence with reg offset, value pair.
 
 Example:
 	ssphy0: ssphy@f9b38000 {
@@ -152,5 +153,10 @@ Example:
 			<&clock_gcc GCC_USB3PHY_PHY_BCR>;
 		reset-names = "phy_reset",
 				"phy_phy_reset";
+		qcom,qmp-phy-override-seq =
+			/* reg val */
+			<0x1f90 0x11
+			 0x1f94 0x46
+			 0x2c78 0x27>;
 
 	};