msm: camera: isp: Sync start SOF of dual VFE in MS mode

In master slave mode, SOF of 2 VFE is bumped up at 1st frame if slave
is already active. Fix race condition in this case which was causing
missed frame ID or duplicate frame ID leading to other issues.

Change-Id: I24a22a8f9c68bdd060c52aad0c9fdab5cbccdb9e
Signed-off-by: Harsh Shah <harshs@codeaurora.org>