dt-bindings: mmc: sdhci-am654: Remove duplicate ti,j721e-sdhci-4bit

The commit 7c7905df ("dt-bindings: mmc: sdhci-am654: fix compatible
for j7200") switched the compatible property from a regular enum to an
more appropriate combinatorial oneOf convention, and in the process has
introduced a duplicate ti,j721e-sdhci-4bit.

This generated the following warning on J721E boards that use the
ti,j721e-sdhci-4bit for two nodes:
 "mmc@4fb0000: compatible: More than one condition true in oneOf schema"
 "mmc@4f98000: compatible: More than one condition true in oneOf schema"

Remove the duplicate to fix this.

Fixes: 7c7905df

 ("dt-bindings: mmc: sdhci-am654: fix compatible for j7200")
Signed-off-by: Suman Anna <s-anna@ti.com>
Link: https://lore.kernel.org/r/20210428230500.19214-1-s-anna@ti.com
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>