mmc: host: Make UHS timing values fully unique

Both of MMC_TIMING_LEGACY and MMC_TIMING_UHS_SDR12 are defined
to 0. And ios->timing is set to MMC_TIMING_LEGACY during power up.
But set_ios can't distinguish these two timing if host support
spec 3.0. Just adjust timing values to be different can resolve
this issue without any other impact.

Reviewed-by: Girish K S <girish.shivananjappa@linaro.org>
Acked-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Kevin Liu <kliu5@marvell.com>
Signed-off-by: Chris Ball <cjb@laptop.org>