ARM: EXYNOS: remove CONFIG_MACH_EXYNOS[4, 5]_DT config options

EXYNOS is now Device Tree (DT) only platform so it makes no sense to have
config options responsible for enabling platform specific DT support.

Moreover the kernel image won't even link if neither CONFIG_MACH_EXYNOS4_DT
nor CONFIG_MACH_EXYNOS5_DT config option is enabled (linker fails with "no
machine record defined" error).

Remove CONFIG_MACH_EXYNOS[4,5]_DT config options and just use the standard
CONFIG_ARCH_EXYNOS[4,5] ones instead.

Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Acked-by: Tomasz Figa <t.figa@samsung.com>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>