msm-camera: Update AVTimer TimeStamps to account for scalar on 8916

AVTimer hardware is configured to generate 27 MHz ticks in 8916 chipset.
So the values read from AVTimer TS registers are in 27 MHz tick units.
To convert them to micro-sec, division by 27 is needed. The TS values
are now obtained in tasklet context as opposed to interrupt context.

CRs-Fixed: 667474
Change-Id: I6cc8463eb2dd23fd2e281415eb9c881c7fc43a7e
Signed-off-by: Venu Yeshala <vyeshala@codeaurora.org>