mmc: dw_mmc: Slot quirk "disable-wp" is deprecated.

Slot quirks "disable-wp" is deprecated.
Instead, use the host quirk "disable-wp".
(Because the slot-node is removed in dt-file.)

Signed-off-by: Jaehoon Chung <jh80.chung@samsung.com>
Tested-by: Sachin Kamat <sachin.kamat@samsung.com>
Acked-by: Seungwon Jeon <tgih.jun@samsung.com>
Reviewed-by: Doug Anderson <dianders@chromium.org>
Tested-by: Doug Anderson <dianders@chromium.org>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>