mmc: sdhci-esdhc-imx: Add HS400 support for i.MX6SLL

i.MX6SLL support MMC up to V5.0, which means support HS400 mode.

Signed-off-by: Haibo Chen <haibo.chen@nxp.com>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Link: https://lore.kernel.org/r/1589527703-19108-1-git-send-email-haibo.chen@nxp.com


Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>