mmc: tegra: Parse and program DQS trim value

Parse and program the HS400 DQS trim value from DT. Program a fallback
value in case the property is missing.

Signed-off-by: Aapo Vienamo <avienamo@nvidia.com>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Acked-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>