mmc: dw_mmc: exynos: fix the suspend/resume issue for exynos5433

Before enabling the clock, dwmmc exynos driver is trying to access the
register. Then the kernel panic can be occurred.

Signed-off-by: Jaehoon Chung <jh80.chung@samsung.com>
Reviewed-by: Chanwoo Choi <cw00.choi@samsung.com>
Tested-by: Chanwoo Choi <cw00.choi@samsung.com>
Cc: stable@vger.kernel.org
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>