powerpc/83xx: Convert existing sdhc nodes to new bindings

- sdhc node renamed to sdhci ("sdhc" name is confusing since SDHC is
  used to name Secure Digital High Capacity cards, while SDHCI is an
  interface).

- Get rid of "fsl,esdhc" compatible entry, it's replaced by the
  "fsl,<chip>-esdhc" scheme;

- Get rid of `model' property.

Signed-off-by: Anton Vorontsov <avorontsov@ru.mvista.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>