watchdog: it87_wdt: 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/it87_wdt.c

···
 
 #include <linux/bits.h>
 #include <linux/dmi.h>
+#include <linux/errno.h>
 #include <linux/init.h>
 #include <linux/io.h>
-#include <linux/kernel.h>
+#include <linux/ioport.h>
 #include <linux/module.h>
 #include <linux/moduleparam.h>
+#include <linux/printk.h>
 #include <linux/types.h>
 #include <linux/watchdog.h>