usb: phy: qusb: Support specifying vdda33 levels from device tree

The specific voltage levels for the vdda33 regulator may vary
depending on the target. Add an optional device tree property to
allow specifying a 3-tuple of voltages for minimum, operating
and maximum voltage levels. The minimum level is used when simply
powering on, whereas the operating level is used when initializing
the PHY.

Change-Id: Ia5d301efdb6964434a01264e7aa19421a41e98ca
Signed-off-by: Jack Pham <jackp@codeaurora.org>