usb: msm_otg: Add LPM support for USB PHY regulators

If USB PHY is used for VBUS/ID detection, PHY internal pull-up resistors
can be used to keep USB lines pulled HIGH during disconnect. In this case
USB PHY regulators can't be turned off, but it can be put into LPM.

Currently we are supporting this capability only for PHY based control.
This patch adds the dtsi flag to allow this capability to put PHY 1P8
and 3P3 regulators in LPM during cable disconnect.

Change-Id: Ic7609a5bd5bedad5a4ca46b6ab9b9c0757e037d1
Signed-off-by: ChandanaKishori Chiluveru <cchilu@codeaurora.org>