watchdog: Don't use "proxy" headers

Update header inclusions to follow IWYU (Include What You Use)
principle.

Note that kernel.h is discouraged to be included as it's written
at the top of that file.

Signed-off-by: Andy Shevchenko <[e-mail]>
Reviewed-by: Guenter Roeck <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Guenter Roeck <[e-mail]>
Signed-off-by: Wim Van Sebroeck <[e-mail]>

drivers/watchdog/watchdog_core.h

···
  *	This material is provided "AS-IS" and at no charge.
  */
 
-#include <linux/hrtimer.h>
+#include <linux/cdev.h>
+#include <linux/device.h>
+#include <linux/hrtimer_types.h>
+#include <linux/init.h>
 #include <linux/kthread.h>
+#include <linux/mutex_types.h>
+#include <linux/types.h>
+#include <linux/watchdog.h>
 
 #define MAX_DOGS	32	/* Maximum number of watchdog devices */
 

drivers/watchdog/watchdog_pretimeout.c

···
 #include <linux/slab.h>
 #include <linux/spinlock.h>
 #include <linux/string.h>
+#include <linux/sysfs.h>
+#include <linux/types.h>
 #include <linux/watchdog.h>
 
 #include "watchdog_core.h"

include/linux/watchdog.h

···
 #ifndef _LINUX_WATCHDOG_H
 #define _LINUX_WATCHDOG_H
 
-
 #include <linux/bitops.h>
-#include <linux/cdev.h>
-#include <linux/device.h>
-#include <linux/kernel.h>
+#include <linux/limits.h>
 #include <linux/notifier.h>
+#include <linux/printk.h>
+#include <linux/types.h>
+
 #include <uapi/linux/watchdog.h>
+
+struct attribute_group;
+struct device;
+struct module;
 
 struct watchdog_ops;
 struct watchdog_device;