ARM: S3C24XX: Fix restart on S3C2442

ARM: S3C24XX: Fix restart on S3C2442

Commit b27b072791dc (ARM: 7265/1: restart: S3C24XX: use new restart hook)
introduced the new restart hook also for the S3C244x cpus, but it
was only defined in the S3C2440 scope, i.e. when CPU_S3C2440 was
selected. Devices using the S3C2442 like the GTA02 normally don't select
this CPU which leads to compilation errors like:
    LD      .tmp_vmlinux1
  arch/arm/mach-s3c2440/built-in.o:(.arch.info.init+0x3c): undefined reference
to `s3c2440_restart'
  make: *** [.tmp_vmlinux1] Error 1

Therefore move the s3c2440_restart function to s3c244x.c which is
common to both cpus and also fix the naming to reflect this.

Reported-and-tested-by: Denis 'GNUtoo' Carikli <GNUtoo@no-log.org>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>