ARM: dts: nomadik: Fix up MMC node names

Fix the node names for the MMC/SD card controller to conform
to the standard node name mmc@..

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://lore.kernel.org/r/20210122222038.2888747-1-linus.walleij@linaro.org

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Signed-off-by: Arnd Bergmann <arnd@arndb.de>