soc: qcom: pil: Properly enable VDD_MSS

<3474e225>("soc: qcom: pil: Reorder votes for vdd_modem to be
proxy voted") misses the call to enable regulator after the values
have been set. Properly enable the regulator here.

Change-Id: Ia7819bd1fa627b1c937a9da53ba255575eaaf354
Signed-off-by: Kyle Yan <kyan@codeaurora.org>