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 <[email protected]>
Reviewed-by: Guenter Roeck <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Guenter Roeck <[email protected]>
Signed-off-by: Wim Van Sebroeck <[email protected]>

Author: andy-shev

drivers/watchdog/it87_wdt.c

@@ -22,11 +22,13 @@
 
 #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>