msm: pil-pronto: Shift enabling regulators to wcnss driver

Currently, the function for configuring the IRIS regulator is
being called from pil-pronto during proxy voting. The regulator
is then turned off in the proxy unvoting function.

Instead, use the notifications which indicate when the proxy
voting/unvoting takes place and configure the IRIS XO from within
the wcnss driver. Doing so is crucial in moving forward with having
a generic PIL/SSR driver for all subsystems.

Change-Id: Ia2512a1197ffbd5e6c60543c60f473052998d759
Signed-off-by: Deepak Katragadda <dkatraga@codeaurora.org>