ARM: samsung: remove HAVE_S3C2410_WATCHDOG and use direct dependencies

A separate Kconfig option HAVE_S3C2410_WATCHDOG for Samsung SoCs is not
really needed and the s3c24xx watchdog driver can depend on Samsung ARM
architectures instead.

The "HAVE_xxx_WATCHDOG" pattern of dependency is not popular and Samsung
platforms are here exceptions.  All others just depend on
CONFIG_ARCH_xxx.

This makes the code slightly smaller without any change in
functionality.

Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Acked-by: Guenter Roeck <linux@roeck-us.net>