msm: camera: isp: Implement synchronization for dual vfe

In case of dual vfe, both vfe hardwares are used for same camera
sensor. There are two tasklets serving irqs from each vfe. This
causes synchronization issues if either one of tasklets is delayed.
To fix this, implement synchronization by using only one vfe
to configure the image and stats buffer for both vfes.

Change-Id: If090bb7526c8d4f544f78e6a9378ebd382253940
Signed-off-by: Senthil Kumar Rajagopal <skrajago@codeaurora.org>