dt-bindings: pinctrl: qcom,sm8450-pinctrl: do not require function on non-GPIOs

Certain pins, like SDcard related, do not have functions and such should
not be required:

  sdc1-clk-pins: 'function' is a required property

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Bjorn Andersson <andersson@kernel.org>
Link: https://lore.kernel.org/r/20220912061746.6311-22-krzysztof.kozlowski@linaro.org
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

Documentation/devicetree/bindings/pinctrl/qcom,sm8450-pinctrl.yaml

@@ -53,7 +53,6 @@ $defs:
     description:
       Pinctrl node's client devices use subnodes for desired pin configuration.
       Client device subnodes use below standard properties.
-    $ref: "qcom,tlmm-common.yaml#/$defs/qcom-tlmm-state"
 
     properties:
       pins:
@@ -105,7 +104,16 @@ $defs:
 
     required:
       - pins
-      - function
+
+    allOf:
+      - $ref: "qcom,tlmm-common.yaml#/$defs/qcom-tlmm-state"
+      - if:
+          properties:
+            pins:
+              pattern: "^gpio([0-9]|[1-9][0-9]|1[0-9][0-9]|20[0-9])$"
+        then:
+          required:
+            - function
 
     additionalProperties: false