dt-bindings: mmc: fsl-imx-esdhc: Add some compatible fallbacks

Currently make dtbs_check shows lots of errors because imx*.dtsi does
not use single compatibles but combinations of them.

Add fallbacks for imx6sll/ull which are useful for U-Boot.

This will significantly reduce noise on make dtbs_check.

Signed-off-by: Andreas Kemnade <andreas@kemnade.info>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20230115195212.2530087-1-andreas@kemnade.info


Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>