msm: camera: change stats offset mapping

In previous implementation we assume stats
pingpong bit are continuos.
However, it can be non-continuous in future chipset.
Therefore, use a bit mapping method to fix this issue.

Change-Id: I85deeb94088b633ec5253c4fb38bcf171b7cbee8
Signed-off-by: Peter Liu <pingchie@codeaurora.org>