dt-bindings: mmc: add Marvell ac5

Add dt bindings for Marvell AC5/X/IM eMMC controller.
This compatibility string covers the differences in the
AC5/X version of the driver: 31-bit bus limitation and
DDR memory starting at address 0x2_0000_0000, which are handled
by usage of a bounce buffer plus a different DMA mask.

Signed-off-by: Elad Nachman <[e-mail]>
Acked-by: Krzysztof Kozlowski <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Ulf Hansson <[e-mail]>

Documentation/devicetree/bindings/mmc/marvell,xenon-sdhci.yaml

···
           - marvell,armada-ap806-sdhci
 
       - items:
-          - const: marvell,armada-ap807-sdhci
+          - enum:
+              - marvell,armada-ap807-sdhci
+              - marvell,ac5-sdhci
           - const: marvell,armada-ap806-sdhci
 
       - items: