ARM: 7246/1: S5P64X0: introduce arch/arm/mach-s5p64x0/common.[ch]

This patch introduces common.[ch] which are used only in the
arch/arm/mach-s5p64x0/ directory. The common.c file merges
the cpu.c, init.c and irq-eint.c files which are used commonly
on S5P64X0 SoCs and the common.h local header file replaces
with plat/s5p6440.h and plat/s5p6450.h files.

Cc: Ben Dooks <ben-linux@fluff.org>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>