dt-bindings: display/msm/hdmi: drop obsolete GPIOs from schema

The commit 68e674b ("drm/msm/hdmi: drop unused GPIO support")
dropped support for obsolete qcom,hdmi-tx-mux-* gpios. They were not
used by any of the upstream platforms. Drop them from the bindings too.

Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Patchwork: https://patchwork.freedesktop.org/patch/651708/
Link: https://lore.kernel.org/r/20250505-fd-hdmi-hpd-v5-1-48541f76318c@oss.qualcomm.com
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>

Author: lumag

Documentation/devicetree/bindings/display/msm/hdmi.yaml

@@ -66,21 +66,6 @@ properties:
     maxItems: 1
     description: hpd pin
 
-  qcom,hdmi-tx-mux-en-gpios:
-    maxItems: 1
-    deprecated: true
-    description: HDMI mux enable pin
-
-  qcom,hdmi-tx-mux-sel-gpios:
-    maxItems: 1
-    deprecated: true
-    description: HDMI mux select pin
-
-  qcom,hdmi-tx-mux-lpm-gpios:
-    maxItems: 1
-    deprecated: true
-    description: HDMI mux lpm pin
-
   '#sound-dai-cells':
     const: 1