arm: exynos: Add header guard for dwmmc.h

Add missing header guard to prevent possible build errors.

Fixes: 77b55e8cfcee ("ARM: exynos: move SoC sources to mach-exynos")
Signed-off-by: Sam Protsenko <semen.protsenko@linaro.org>
Signed-off-by: Minkyu Kang <mk7.kang@samsung.com>
1 file changed