dt-bindings: mmc: sdhci-of-dwcmhsc: Add T-Head TH1520 support

Add compatible value for the T-Head TH1520 dwcmshc controller.
Acked-by: Guo Ren <guoren@kernel.org>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Drew Fustini <dfustini@baylibre.com>
Link: https://lore.kernel.org/r/20231109-th1520-mmc-v5-1-018bd039cf17@baylibre.comSigned-off-by: Ulf Hansson <ulf.hansson@linaro.org>

Documentation/devicetree/bindings/mmc/snps,dwcmshc-sdhci.yaml

@@ -19,6 +19,7 @@ properties:
       - rockchip,rk3568-dwcmshc
       - rockchip,rk3588-dwcmshc
       - snps,dwcmshc-sdhci
+      - thead,th1520-dwcmshc
 
   reg:
     maxItems: 1