msm: camera: isp: Fix double add list corruption

In dual VFE usecase, buffer is shared by both VFE and get_cnt and put_cnt
are used for sync. Direct buf_done() from drop_frame() or return_empty()
causes the buffer to be released prematurely causing list_corruption by
double add. Each VFE should first update put_cnt and then do buf_done()
if count is 2. This should avoid double add.
Also share_list needs to be cleared of all entries on stop_axi so there
are no stale entries which might cause double add. Flush_buf() will
clear the list.

Change-Id: I48f11db69af7a3350144c02511c4199adf1985bb
Signed-off-by: Harsh Shah <harshs@codeaurora.org>