Input: sentelic - minor code cleanup

Input: sentelic - minor code cleanup

BugLink: http://bugs.launchpad.net/bugs/969334

Improve code readability by converting yet another magic number into a
pre-defined constant.

Signed-off-by: Tai-hwa Liang <avatar@sentelic.com>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>
(cherry picked from commit 7b85f73d0461188aa397d428e6c53419ebfd86b4)

Signed-off-by: Eric Miao <eric.miao@canonical.com>
Acked-by: Leann Ogasawara <leann.ogasawara@canonical.com>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>