mmc: sdhci-esdhc-imx: add device tree probe support

The patch adds device tree probe support for sdhci-esdhc-imx driver.

Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
Cc: Wolfram Sang <w.sang@pengutronix.de>
Cc: Chris Ball <cjb@laptop.org>
Cc: Grant Likely <grant.likely@secretlab.ca>
Acked-by: Grant Likely <grant.likely@secretlab.ca>
Acked-by: Chris Ball <cjb@laptop.org>