ARM: exynos: move SoC sources to mach-exynos

Move arch/arm/cpu/armv7/exynos/* to arch/arm/mach-exynos/* to allow
reuse of existing code for ARMv8 based Exynos platforms.

Cc: Minkyu Kang <mk7.kang@samsung.com>
Cc: Albert Aribaud <albert.u.boot@aribaud.net>
Cc: Masahiro Yamada <yamada.m@jp.panasonic.com>
Signed-off-by: Thomas Abraham <thomas.ab@samsung.com>
Reviewed-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Tested-by: Przemyslaw Marczak <p.marczak@samsung.com>
Acked-by: Przemyslaw Marczak <p.marczak@samsung.com>
Signed-off-by: Minkyu Kang <mk7.kang@samsung.com>