msm: camera: vote for AHB clock

AHB clock is needed to access the hardware registers.
Hence add support for voting camera AHB clock.

Change-Id: I6e3dcce608b39679c2e6b4ea406612433a7d9f4f
Signed-off-by: Lakshmi Narayana Kalavala <lkalaval@codeaurora.org>