arm: mvebu: clearfog: Detect MMC vs SDHC and fixup fdt

arm: mvebu: clearfog: Detect MMC vs SDHC and fixup fdt

[upstream of vendor commit 19a96f7c40a8fc1d0a6546ac2418d966e5840a99]

The Clearfog devices have only one SDHC device. This is either eMMC if
it is populated on the SOM or SDHC if not. The Linux device tree assumes
the SDHC case. Detect if the device is an eMMC and fixup the device-tree
so it will be detected by Linux.

Ported from vendor repo at https://github.com/SolidRun/u-boot

Signed-off-by: Martin Rowe <martin.p.rowe@gmail.com>
Reviewed-by: Stefan Roese <sr@denx.de>