mmc: dw_mmc: let device core setup the default pin configuration

With device core now able to setup the default pin configuration,
the pin configuration code based on the deprecated Samsung specific
gpio bindings is removed.

Signed-off-by: Thomas Abraham <thomas.abraham@linaro.org>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Doug Anderson <dianders@chromium.org>
Tested-by: Doug Anderson <dianders@chromium.org>
Acked-by: Seungwon Jeon <tgih.jun@samsung.com>
Signed-off-by: Chris Ball <cjb@laptop.org>