[WATCHDOG] removed unused #include <version.h>

The drivers below do not use LINUX_VERSION_CODE nor KERNEL_VERSION.
  drivers/watchdog/pc87413_wdt.c

This patch removes the said #include <version.h>.

Signed-off-by: Huang Weiyi <weiyi.huang@gmail.com>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>