ipmi/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>
Message-Id: <37daa028845d90ee77f1e547121a051a983fec2e.1667647002.git.christophe.jaillet@wanadoo.fr>
Signed-off-by: Corey Minyard <cminyard@mvista.com>