mmc: sdhci-esdhc-imx: manually reset MIX_CTRL for usdhc
mmc: sdhci-esdhc-imx: manually reset MIX_CTRL for usdhc

It's another violation to SDHC spec that software reset on usdhc
does not reset MIX_CTRL register.  Have to do it manually, otherwise
the preserving of the register bits (e.g. AC23EN) may cause mmc card
fail to be initialized.

Signed-off-by: Shawn Guo <912cf7eb7d8018e2943586ae6657d21fd4e38239@linaro.org>
Tested-by: Dirk Behme <65191830245723325aed938dddb6d81810e13fc4@de.bosch.com>
Signed-off-by: Chris Ball <6ca7faee6ca9a094b1ee341f11b840a5608a8746@laptop.org>

TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas