Since v2.80a, dwmmc controller introduced the card write threshold for
HS400 mode. So CardThrCtl can be supported during write operation, not
only read operation.
(Note: Only use the write threshold when mode is HS400.)

To use more compatible, removed "_rd_" from function name.
Signed-off-by: Jaehoon Chung <jh80.chung@samsung.com>
Reviewed-by: Shawn Lin <shawn.lin@rock-chips.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>