mmc: sdhci-esdhc-imx: add imx6sx support
mmc: sdhci-esdhc-imx: add imx6sx support

The imx6sx usdhc is derived from imx6sl, the difference is minor.
imx6sx have the errata ESDHC_FLAG_ERR004536 fixed.
So introduce a new compatible string for imx6sx to distinguish them.

Signed-off-by: Dong Aisheng <f8b72116bf80189a70941b53a10a3d3b2650c711@freescale.com>
Signed-off-by: Ulf Hansson <fe47b31f388f85ce6ddf64bf3a0cf6b46077d0e6@linaro.org>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs