Reseting Endpoint state must be handled in high-level code rather than automatically

[xross]

For example: https://github.com/xmos/lib_xua/blob/17ed636a74299a7dae51dfd3f6797a3111db9eaf/lib_xua/src/core/endpoint0/xua_endpoint0.c#L655

This requirement should either be properly documented or handled automatically.