dt-bindings: intel: Add Agilex eMMC support

Agilex devkit support a separate eMMC daughter card. Document Agilex
eMMC daughter board compatible.

[dinguyen] becauce of patch 1cb8486 ("dt-bindings: arm: altera: combine Intel's SoCFPGA into altera.yaml"),
I moved the change to altera.yaml file.

Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@oss.qualcomm.com>
Signed-off-by: Ng Tze Yee <tzeyee.ng@altera.com>
Signed-off-by: Dinh Nguyen <dinguyen@kernel.org>

Author: Ng Tze Yee

Documentation/devicetree/bindings/arm/altera.yaml

@@ -90,6 +90,7 @@ properties:
               - intel,n5x-socdk
               - intel,socfpga-agilex-n6000
               - intel,socfpga-agilex-socdk
+              - intel,socfpga-agilex-socdk-emmc
           - const: intel,socfpga-agilex
 
       - description: Agilex3 boards