drm/msm: add power handle driver for msm

The power handle driver parses the regulator and
clocks present on certain device node and it votes/enables
the clock when client request for it. Multiple clients
can request for enable/disable at the same time. It handles
the reference counting logic to avoid removal vote from
other client. It also supports the register bus driver
voting. Data bus driver support is still missing.

Change-Id: I030f302dce82508e89006cc034d825a071fe9967
Signed-off-by: Dhaval Patel <pdhaval@codeaurora.org>