mmc: sdhci-esdhc-imx: wait for data transfer completion before reset

On IMX7ULP platforms, certain SD cards (e.g. Kingston Canvas Go! Plus)
cause system hangs and reboots during manual tuning. These cards exhibit
large gaps (~16us) between tuning command response and data transmission.
When cmd CRC errors occur during tuning, the code assumes data errors even
tuning data hasn't been fully received and then reset host data circuit.

Per IMX7ULP reference manual, reset operations (RESET_DATA/ALL) need to
make sure no active data transfers. Previously, resetting while data was
in-flight would clear data circuit, including ADMA/SDMA address, causing
data to be transmitted to incorrect memory address. This patch adds
polling for data transfer completion before executing resets.

Signed-off-by: Luke Wang <ziniu.wang_1@nxp.com>
Reviewed-by: Bough Chen <haibo.chen@nxp.com>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

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