arm64: dts: qcom: msm8916: Set 'xo_board' as ref clock of the DSI PHY

Add 'xo_board' as ref clock for the DSI PHYs, it was previously
hardcoded in the PLL 'driver' for the 28nm PHY.
Signed-off-by: Matthias Kaehlcke <mka@chromium.org>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Stephen Boyd <swboyd@chromium.org>
Signed-off-by: Andy Gross <agross@kernel.org>

arch/arm64/boot/dts/qcom/msm8916.dtsi

@@ -1024,8 +1024,9 @@ dsi_phy0: dsi-phy@1a98300 {
 				#clock-cells = <1>;
 				#phy-cells = <0>;
 
-				clocks = <&gcc GCC_MDSS_AHB_CLK>;
-				clock-names = "iface";
+				clocks = <&gcc GCC_MDSS_AHB_CLK>,
+					 <&xo_board>;
+				clock-names = "iface", "ref";
 			};
 		};