dt-bindings: mmc: sdhci-atmel: Convert to json schema

dt-bindings: mmc: sdhci-atmel: Convert to json schema

Convert sdhci-atmel documentation to yaml format. The new file will inherit
from sdhci-common.yaml.

Note: Add microchip,sama7g5-sdhci to compatible list as we already use it
in the DT.

Signed-off-by: Dharma Balasubiramani <dharma.b@microchip.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20240902-atmel-sdhci-v4-1-96912fab6b2d@microchip.com
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>