msm: pil-riva: Proxy vote for L23

L23 supplies the power for the PLL that RIVA uses during boot.
Proxy vote for the regulator until RIVA is up enough to put in
its own vote. Otherwise we may turn off L23 while RIVA is just
booting and kill the processor. Move to using a workqueue instead
of a timer for the proxy timeout so that regulator APIs can be
used.

Change-Id: I2303f623803b44e993db323ca08c5e87144d7403
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>