mmc: sdhci: Disable re-tuning for HS400

Re-tuning for HS400 mode must be done in HS200
mode. Currently there is no support for that.
That needs to be reflected in the code.
Specifically, if tuning is executed in HS400 mode
then return an error, and do not start the
tuning timer if HS200 tuning is being done prior
to switching to HS400.

Note that periodic re-tuning is not expected
to be needed for HS400 but re-tuning is still
needed after the host controller has lost power.
In the case of suspend/resume that is not necessary
because the card is fully re-initialised. That
just leaves runtime suspend/resume with no support
for HS400 re-tuning.

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