usb: dwc3: Enable multiple UDC support

Allow binding between UDC and gadget driver to take
place based on usb-core-id.Since only one instance of
USB power-supply can exist, user can pass qcom,psy-not-used
with other instances of dwc3 which will be by default in
host mode. User can change the mode later using sysfs.
Eg:
 echo peripheral > /sys/devices/soc/7600000.hsusb/mode (Device)
 echo host > /sys/devices/soc/7600000.hsusb/mode (Host)
 echo none > /sys/devices/soc/7600000.hsusb/mode (Disconnect)

Change-Id: I965ba0950e9ef647d8e8fec0b2f4e0c7987329a6
Signed-off-by: Pratham Pratap <prathampratap@codeaurora.org>