mmc: dw_mmc: fix card threshold control configuration

Card write threshold control is supposed to be set since controller
version 2.80a for data write in HS400 mode and data read in
HS200/HS400/SDR104 mode. However the current code returns without
configuring it in the case of data writing in HS400 mode.
Meanwhile the patch fixes that the current code goes to
'disable' when doing data reading in HS400 mode.

Fixes: 7e4bf1bc ("mmc: dw_mmc: add the card write threshold for HS400 mode")
Signed-off-by: Qing Xia <xiaqing17@hisilicon.com>
Cc: stable@vger.kernel.org # v4.8+
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>