This patch is the first part of fixing the EHCI driver to queue
interrupt transactions, handle larger requests, and basically treat
interrupt as just "bulk that lives on the periodic schedule".  One
more patch should wrap that up.

     qh processing cleanup
	- split "append tds to qh" logic out of "put on async schedule",
	  so it can be used with "put on periodic schedule" too
     interrupt transfer cleanup
	- save rest of scheduling params in the qh
	- calculate scheduling params only once
     other cleanup
	- use new container_of()
	- minor code shrinkage (avoid pipe bitops, conditionals, etc)
	- rename variable (will track endpoints, not urbs)
	- free_config() logic