msm: pil-modem: Move to common proxy voting

Remove the boiler plate workqueue and proxy voting code and move
to the common proxy infrastructure that the core pil code
provides. This has the added benefit of fixing any issues where
suspend happens before the proxy vote is removed.

Change-Id: Id739d14af6ffc3c6129aa25cb59ca99b22491316
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>