USB: MUSB changes for 3.4

Here are a set of changes to the MUSB driver. In summary we have
a patch making modules behave better, there's a fix on debugfs'
error path, a small change removing an unnecessary pm_runtime
call on musb_shutdown() and a fix to relesect the endpoint in
Interrupt context.

This last patch is needed because we must drop musb's lock when
calling request->complete() and that could cause problems if another
thread queues a request and ends up changing MUSB_INDEX register.