arm64: Enable ARMv8 based exynos7 SoC support

This patch adds the necessary Kconfig entries to enable
support for the ARMv8 based exynos7 SoC. It also enables
RTC, WDT and Pinctrl for exynos7 SoC.

Signed-off-by: Alim Akhtar <alim.akhtar@samsung.com>
Signed-off-by: Naveen Krishna Ch <naveenkrishna.ch@gmail.com>
Signed-off-by: Abhilash Kesavan <a.kesavan@samsung.com>
Reviewed-by: Thomas Abraham <thomas.ab@samsung.com>
Tested-by: Thomas Abraham <thomas.ab@samsung.com>
Cc: Rob Herring <robh@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Kukjin Kim <kgene@kernel.org>