raw_gadget: fix MSC recovery after endpoint halt

Allow opt-in DCDs to queue transfers behind a halted endpoint without changing hardware DCD behavior.

Retry dummy_hcd's transient EP_SET_HALT failure, queue MSC BOT status and recovery requests behind the halt, and clean up Raw Gadget endpoint workers across bus reset.

Signed-off-by: Zixun LI <admin@hifiphile.com>