USB: OTG: Implement aggressive power management while going to LPM

USB HW can turn off the voltage regulators, OTG comparators and can
enable PHY retention mode as a part of aggressive power management while
going to LPM provided that PMIC has capability to detect the VBUS/ID
change and doesn't have any leakage currents while turning off the
regulators.
8960 doesn't have the leakage currents and PM8921 has capability to
detect VBUS and ID change. Hence Implement the aggressive power management
for 8960.
Initialize the PHY capabilities to support aggressive power management
in the probe and use it to implement aggressive power management.

Change-Id: If3e966b0c81b3588caa5ca93e9e877e4f777892c
Signed-off-by: Anji jonnala <anjir@codeaurora.org>