watchdog: Include <linux/kstrtox.h> when appropriate

The kstrto<something>() functions have been moved from kernel.h to
kstrtox.h.

So, in order to eventually remove <linux/kernel.h> from <linux/watchdog.h>,
include the latter directly in the appropriate files.

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/08fd5512e569558231247515c04c8596a1d11004.1667646547.git.christophe.jaillet@wanadoo.fr


Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>