dt-bindings: mmc: sdhci-msm: cleanup style

Drop unnecessary quotes from $ref.
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20221204094717.74016-3-krzysztof.kozlowski@linaro.orgSigned-off-by: Ulf Hansson <ulf.hansson@linaro.org>

Documentation/devicetree/bindings/mmc/sdhci-msm.yaml

 # SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
-
 %YAML 1.2
 ---
-$id: "http://devicetree.org/schemas/mmc/sdhci-msm.yaml#"
-$schema: "http://devicetree.org/meta-schemas/core.yaml#"
+$id: http://devicetree.org/schemas/mmc/sdhci-msm.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
 
 title: Qualcomm SDHCI controller (sdhci-msm)