usb: dwc3: core: Notify current USB mode to USB3 PHY as well

Driver currently notifies only USB2 PHY on USB mode change.
Extend this to USB3 PHY so that PHY drivers based on the
mode can release system resources - clocks, regulators etc.
Additionally Qualcomm QMP and QUSB2 PHY drivers need to
override VBUS signal in PHY wrapper in device mode as USB
VBUS line is not connected to PHYs. Also, remove NULL checks
for PHY when calling phy_set_mode as PHY ops already check this.

Signed-off-by: Manu Gautam <mgautam@codeaurora.org>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>