msm: camera: debugfs to update clk rates dynamically

This change provides provision to read the supported clk
rates for each of the hardwares and one can vote for one
of the supported clk levels before streamon.

Change-Id: I9626fb87b6a72b70b4479562b6f50b31b85263be
Signed-off-by: Karthik Anantha Ram <kartanan@codeaurora.org>