asus-laptop: return proper error for store_ledd if write_acpi_int fail

In current implementation, store_ledd() does not return error if
write_acpi_int fail.  This patch fixes it by return -ENODEV if
write_acpi_int fail.

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>