usbd: Exit in case of charger mode.

UsbGadget hal is not expected run in charger mode.
This should fix the following errors in charger mode:

[   86.609578] c4    612 init: Received control message 'interface_start' for 'android.hardware.usb.gadget@1.0::IUsbGadget/default' from pid: 565 (/system/bin/hwservicemanager)
[   86.618236] c7      1 init: Could not find 'android.hardware.usb.gadget@1.0::IUsbGadget/default' for ctl.interface_start

Bug: 135566354
Test: Manually verified that usbd exits early in charger mode.
Change-Id: I3ba5be883c49e5ca3e4dad4443528e4eee8b25b9
Merged-In: I3ba5be883c49e5ca3e4dad4443528e4eee8b25b9