ARM: dts: msm: add fixed-regulator to supply USB2 VBUS on Lahaina HHG

Lahaina HHG device has a built-in joystick connected on USB2 port, the
VBUS is supplied by a fixed-regulator controlled by PM8350 GPIO8 and its
output voltage needs to be enabled always. Add the regulator device node
and config it as always-on.

Change-Id: I4877be73294939e4823965795a00053ebd84e572