Now, no dw_mmc variant drivers use this callback, let's
remove it.
Signed-off-by: NShawn Lin <shawn.lin@rock-chips.com>
Signed-off-by: NJaehoon Chung <jh80.chung@samsung.com>
Signed-off-by: NUlf Hansson <ulf.hansson@linaro.org>