mmc: renesas_sdhi: Change HW adjustment register according to speed mode

SCC is used for SDR104/HS200/HS400. We need to change SCC_DT2FF
according to the mode. If it is inappropriate, CRC error tends to occur.

This adds variable "tap_hs400" for HS400 mode and configures SCC_DT2FF
as needed.

Signed-off-by: Takeshi Saito <takeshi.saito.xv@renesas.com>
[wsa: rebased to upstream and updated commit message]
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Reviewed-by: Niklas Söderlund <niklas.soderlund@ragnatech.se>
Tested-by: Marek Vasut <marek.vasut@gmail.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>