usb: phy: qusb: Remove updating VBUS status from QUSB PHY driver

This change removes updating VBUS status from QUSB PHY driver using
QSCRATCH register. New change would be adding same functionality from
USB controller driver.

- It also updates devicetree documentation and existing supported
MSM/MDM platforms' USB device node property to accommodate above changes.

CRs-Fixed: 1046503
Change-Id: I4573a077bb455ebe3750ab76a91d2593d7e94ea5
Signed-off-by: Mayank Rana <mrana@codeaurora.org>