msm: camera: isp: Update the reported_req_id correctly

The request id is updated to 0 when the substate is
BUBBLE, then the original request id can't be notified
to UMD, since the reported_req_id is already updated to
the original request id. This change updateds the
reported_req_id only when the final request id is
valid.

CRs-Fixed: 2932602
Change-Id: Ib30f849782283c647f784cfb0deb49bee3d04287
Signed-off-by: Depeng Shao <depengs@codeaurora.org>