ANDROID: GKI: extcon: Fix Add usage of blocking notifier chain

The previous partial cherry-pick commit ea6eb0f3 missed out some
code that's needed for functionality. So, pick that up too.

Change-Id: I0e8e3b29d169ca833f85e42d2df98dd8380cbf46
Signed-off-by: Mayank Rana <mrana@codeaurora.org>
Signed-off-by: Jack Pham <jackp@codeaurora.org>
Bug: 150893404
(cherry picked from commit 9dce266c)
Signed-off-by: Saravana Kannan <saravanak@google.com>