ACPI: watchdog: fix kernel-doc warnings

Fix kernel-doc warnings found when using "W=1".

acpi_watchdog.c:85: warning: This comment starts with '/**', but isn't a kernel-doc comment. Refer Documentation/doc-guide/kernel-doc.rst
acpi_watchdog.c:85: warning: missing initial short description on line:
 * Returns true if this system should prefer ACPI based watchdog instead of
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/acpi/acpi_watchdog.c

@@ -81,7 +81,7 @@ static const struct acpi_table_wdat *acpi_watchdog_get_wdat(void)
 	return wdat;
 }
 
-/**
+/*
  * Returns true if this system should prefer ACPI based watchdog instead of
  * the native one (which are typically the same hardware).
  */