ARM: SAMSUNG: local watchdog-reset header in mach-s3c64xx

This patch moves watchdog-reset header file into mach-s3c64xx.
Because it is not used for others except mach-s3c64xx.

Cc: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Signed-off-by: Kukjin Kim <kgene@kernel.org>