staging: line6: Changed strict_strtoul() to kstrtou8() in pod_set_channel()

Changed strict_strtoul() to kstrtou() in pod_set_channel() to take changes in
pod_send_channel() into account.

Signed-off-by: Johannes Thumshirn <morbidrsa@googlemail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>