asus-laptop: fix incorrect return value for write_acpi_int_ret if handle is NULL

According to the comments of write_acpi_int_ret(), write_acpi_int_ret()
should return 0 if write is successful, -1 else.  Thus if handle is NULL,
the write does not happen, it should return -1.
Signed-off-by: Axel Lin <axel.lin@gmail.com>
Cc: Matthew Garrett <mjg@redhat.com>
Cc: Corentin Chary <corentincj@iksaif.net>
Cc: Alan Jenkins <alan-jenkins@tuffmail.co.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Matthew Garrett <mjg@redhat.com>

drivers/platform/x86/asus-laptop.c

@@ -297,7 +297,7 @@ static int write_acpi_int_ret(acpi_handle handle, const char *method, int val,
 	acpi_status status;
 
 	if (!handle)
-		return 0;
+		return -1;
 
 	params.count = 1;
 	params.pointer = &in_obj;