mmc: sdhci-esdhc-imx: usdhc does not have missing card interrupt issue

The usdhc does not have missing card interrupt issue, so don't execute
workaround for usdhc.

Signed-off-by: Dong Aisheng <aisheng.dong@freescale.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>