msm: camera: sync: Report error if getting sync obj reference fails

If we fail to get reference for a sync object propagate the
error directly, there is no necessity to invoke the sync signal
procedure.

Change-Id: I3799018db58b1bb04114c0fb45a967be89f90f06
Signed-off-by: Karthik Anantha Ram <kartanan@codeaurora.org>