ARM: dts: bcm283x: 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: Stefan Wahren <stefan.wahren@i2se.com>
Link: https://lore.kernel.org/r/1622981777-5023-2-git-send-email-stefan.wahren@i2se.com


Signed-off-by: Nicolas Saenz Julienne <nsaenz@kernel.org>