mmc: sdhci-esdhc-imx: Reset before sending tuning command for manual tuning

According to IC suggestion, everytime before sending the tuning command,
need to reset the usdhc, so to reset the tuning circuit, to let every
tuning command work well for the manual tuning method. For standard tuning
method, IC already add the reset operation in the hardware logic.

Signed-off-by: Haibo Chen <haibo.chen@nxp.com>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Link: https://lore.kernel.org/r/1597135057-22272-1-git-send-email-haibo.chen@nxp.com
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>