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

This reverts commit 3b8d7321ed4b8511e17048303b806ffcc2806077, which
brings back commit 428aac8a81058e2303677a8fbf26670229e51d3a as it should
be working for the 3.13-rc1 merge window now that Alan's other fixes are
here in the tree already.

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