SnapdragonCamera: Add the developer option for instant capture

A developer option is added to support instant capture feature
in the camera HAL. Once option is enabled, Snapdragon camera
application will take a snapshot as soon as it is resumed from
the lock screen by pressing power button twice. For this to
work, user also needs to enable "Press power button twice
for camera" under display setting.

Change-Id: I84794759ee1edc9424c37b71bd0c2b761a77bee1
CRs-Fixed: 970691
6 files changed