dt-bindings: msm: disp: remove bus from dpu bindings

Driver and dts has been already adjusted and bus moved out of dpu, let's
update also dt-bindings.

Fixes warnings as:
arch/arm64/boot/dts/qcom/sdm845-oneplus-fajita.dt.yaml: mdss
@ae00000: clock-names: ['iface', 'core'] is too short
        From schema: Documentation/devicetree/bindings/display/msm/dpu-sdm845.yaml

Ref: https://lore.kernel.org/all/20210803101657.1072358-1-dmitry.baryshkov@linaro.org/Signed-off-by: David Heidelberg <david@ixit.cz>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20211220184220.86328-1-david@ixit.cz

Documentation/devicetree/bindings/display/msm/dpu-sdm845.yaml

@@ -31,13 +31,11 @@ properties:
   clocks:
     items:
       - description: Display AHB clock from gcc
-      - description: Display AXI clock
       - description: Display core clock
 
   clock-names:
     items:
       - const: iface
-      - const: bus
       - const: core
 
   interrupts:
@@ -160,9 +158,8 @@ examples:
           power-domains = <&dispcc MDSS_GDSC>;
 
           clocks = <&gcc GCC_DISP_AHB_CLK>,
-                   <&gcc GCC_DISP_AXI_CLK>,
                    <&dispcc DISP_CC_MDSS_MDP_CLK>;
-          clock-names = "iface", "bus", "core";
+          clock-names = "iface", "core";
 
           interrupts = <GIC_SPI 83 IRQ_TYPE_LEVEL_HIGH>;
           interrupt-controller;