mmc: sdhci: Add support for O2 hardware tuning

Add hardware tuning function instead of software tuning because O2/Bayhub
SD host controller support hardware tuning.

Signed-off-by: ernest.zhang <ernest.zhang@bayhubtech.com>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>