net: ar8327: replace sprintf() by scnprintf()

Import from https://chromium.googlesource.com/chromiumos/third_party/kernel/+/fd0c41c7b9327ce003f44df38ce42556fb177b17%5E%21/#F0
Signed-off-by: Pavel Kubelun <be.dissent@gmail.com>
CHROMIUM: drivers: ar8216: replace sprintf() by scnprintf()

BUG=chrome-os-partner:33096
TEST=none

Change-Id: Ib82035c9f2769a86d3e90f9573a09e5700ff5676
Signed-off-by: Mathieu Olivari <mathieu@codeaurora.org>
Reviewed-on: https://chromium-review.googlesource.com/232829
Reviewed-by: Matthias Kaehlcke <mka@chromium.org>
Tested-by: Toshi Kikuchi <toshik@chromium.org>
Reviewed-by: Toshi Kikuchi <toshik@chromium.org>