Contain USB_GADGET_DELAYED_STATUS within composite framework

[xairy]

This is not an issue in Raw Gadget, but rather an inconsistency within the Linux kernel USB Gadget subsystem. It was discovered while investigating and fixing #45.

Quoting the related Linux kernel commit:

The proper solution to this issue would be to contain USB_GADGET_DELAYED_STATUS within the composite framework and make all UDC drivers to not complete the status stage for 0-length requests on their own.

Unfortunately, there is quite a few UDC drivers that need to get fixed and the required changes for some of them are not trivial.