Since v2.80a, dwmmc controller introduced the card write threshold for
HS200 & HS400 mode. So CardThrCtl can be supported during write operation, not
only read operation.
Signed-off-by: Jason Zhu <jason.zhu@rock-chips.com>
Change-Id: I7f345660107c2978d2f874d36f2dffd2acdfbcb6