0ca0940f01: Make USB Charging default value configurable per device
A reasonable default assumption for a user would be that they can plug their device into a USB AC adapter and it will charge with as much current as it reasonably can. With the previous default, an AC adapter will only do 100mA, basically a trickle charge.
Make this configurable default per-device, so as not to break old devices without testing.
Define TARGET_USB_CHARGING_DEFAULT to USB_CHARGING_FORCE to use the new default.