mmc: dw_mmc: exynos: Remove code for wp-gpios

The exynos code claimed the write protect with devm_gpio_request() but
never did anything with it.  That meant that anyone using a write
protect GPIO would effectively be write protected all the time.

The handling for wp-gpios belongs in the main dw_mmc driver and has
been moved there.

Signed-off-by: Doug Anderson <dianders@chromium.org>
Acked-by: Seungwon Jeon <tgih.jun@samsung.com>
Acked-by: Olof Johansson <olof@lixom.net>
Signed-off-by: Chris Ball <cjb@laptop.org>