msm: camera: isp: Increment bubble frame count correctly

In certain scenarios due to tasklet congestion,
back to back sof were seen and this will lead to
wrong bubble frame count. As a result, after
moving request from active list, same request
will be re-applied. Hence increment bubble frame
count only if last sof timestamp is different
from current sof timestamp.

CRs-Fixed: 2831372
Change-Id: I8977233c001e2f31f4c7bf5e86d95b1849023d86
Signed-off-by: Shravya Samala <shravyas@codeaurora.org>