Revert "USB: EHCI: support running URB giveback in tasklet context"

This reverts commit 428aac8a.

This isn't quite ready for 3.12, we need some more EHCI driver changes
that are just now showing up.  So revert this for now, and queue it up
later for 3.13.

Reported-by: Alan Stern <stern@rowland.harvard.edu>
Cc: Ming Lei <ming.lei@canonical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>