msm: camera: isp: Remove buffer queue shared list

Remove the shared list of buffer queue that is used in case of
dual vfe. Whenever a buffer is dequeued from the buffer queue
program it on both vfe and ensure that buffer is dequeued only
once by compositing the buf done irq.
Also, program scratch buffer for stats stream

Change-Id: I96cd0a97b24bf6bc0223cbee8d1fc6bf2ecc7c49
Signed-off-by: Harsh Shah <harshs@codeaurora.org>
Signed-off-by: Shubhraprakash Das <sadas@codeaurora.org>
Signed-off-by: Jing Zhou <jzhou70@codeaurora.org>