msm: pil-q6v4: Proxy vote for L23

L23 supplies the power for the PLLs that the modem uses during
boot. Proxy vote for the regulator until the modem is up enough
to put in its own vote. Otherwise we may turn off L23 while the
modem is just booting and kill the processor. Move to using
workqueues instead of timers due to regulator APIs.

Change-Id: I54c9fa025c094d4e12dbbd3212cefebe5744f8f7
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>