usb: phy: msm: Remove USB power_supply

Now that we use extcon for USB and USB_HOST cable connection
notification, it is no longer required to provide the usb
power_supply object in order to receive set property
notifications. Going forward the usb_psy will be maintained
by the charger driver(s) instead.

Change-Id: Ie209dc6f88ad9cfb31fbe29b074dc911909211f6
Signed-off-by: Ajay Agarwal <ajaya@codeaurora.org>