msm: camera: req_mgr: Add sync mode flag in req_mgr uapi header

To support dual camera and to handle requests in
sync or non-sync mode, sync_mode flag is required
while scheduling requests. Add macro definitions
for different sync modes and flag in uapi structure.

Change-Id: I69a26e2fdf34959f6440d2330c6acd9d2d1d6a8c
Signed-off-by: Pavan Kumar Chilamkurthi <pchilamk@codeaurora.org>