ARM: S5P6442: Update Kconfig and Makefiles

Updates arch/arm Kconfig and Makefile for building the S5P6442 support.
Also modifies the plat-s5p Kconfig file to include the support for plat-s5p
for S5P6442.

Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>
Signed-off-by: Ben Dooks <ben-linux@fluff.org>