ARM: SAMSUNG: Make WDT driver dependency SoC specific instead of machine specific

This patch moves the dependency of watchdog timer driver from MACH_XXX(board)
to ARCH_XXX(SoC). This will enable all machines using Samsung S3C64XX and S5P
SoCs to use the WDT driver by default.

Signed-off-by: Banajit Goswami <banajit.g@samsung.com>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>
Conflicts:

	arch/arm/Kconfig
	arch/arm/mach-s3c64xx/Kconfig
	arch/arm/mach-s5p6442/Kconfig
	arch/arm/mach-s5pc100/Kconfig