mmc: fsl_esdhc_imx: add OF_PLATDATA support

In order to reduce the footprint of SPL by removing dtb and library
overhead, add OF_PLATDATA support to fsl_esdhc_imx. This initial
approach does not support card detection, which will be enabled after
adding OF_PLATDATA support to GPIO.

Signed-off-by: Walter Lozano <walter.lozano@collabora.com>
Reviewed-by: Simon Glass <sjg@chromium.org>