ARM: EXYNOS: Remove Exynos4415 arch code (SoC not supported anymore)

Support for Exynos4415 is going away because there are no internal nor
external users.

Since commit 46dcf0ff ("ARM: dts: exynos: Remove exynos4415.dtsi"),
the platform cannot be instantiated so remove also the mach code.

Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Acked-by: Kukjin Kim <kgene@kernel.org>
Reviewed-by: Chanwoo Choi <cw00.choi@samsung.com>