msm: camera: ife: calculate boot timestamp at csid SOF

This change is to avoid passing zero as boot timestamp for second
SOF onwards. If boot timestamp is not consumed for first SOF, it
will be read as zero at ISP context layer.
With this change, the logic to calculate accurate boot timestamp
is moved at csid core.

Change-Id: Icafd2cd8b9061cc935c977062cce573eb27a2597
Signed-off-by: Alok Pandey <akumarpa@codeaurora.org>