ARM: EXYNOS: Fix EXYNOS_DEV_DMA Kconfig entry

Commit 20ef9e08 ("ARM: EXYNOS: Support DMA for EXYNOS5250 SoC")
renamed EXYNOS4_DEV_DMA to EXYNOS_DEV_DMA. But some machine entries
still had EXYNOS4_DEV_DMA. Changed them to EXYNOS_DEV_DMA.

Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>