mmc: sdhci-esdhc-imx: create struct esdhc_soc_data

Create a struct esdhc_soc_data with moving 'flags' field from
pltfm_imx_data into it, and pass the pointer of this SoC specific data
structure through of_device_id.data directly, so that the translation
from enum imx_esdhc_type to flags can be saved.

With the change, enum imx_esdhc_type can be eliminated, since we can
implement the is_imx*_esdhc() by checking the esdhc_soc_data pointer.
The unused is_imx35_esdhc() and is_imx51_esdhc() are also removed, and the
others are kept there as we will need to use them to handle some small
register differences later, where use of new flags might be a little
overkilled.

Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
Acked-by: Dong Aisheng <b29396@freescale.com>
Signed-off-by: Chris Ball <cjb@laptop.org>