ARM: S5P64X0: Update Kconfig and Makefile

This patch updates the Kconfig and Makefile for the S5P6440 and S5P6450
machines. It also updates arch/arm/ Kconfig and Makefile to include for
support ARCH_S5P64X0 with one kernel image.

Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>