USB: EHCI: Fix resume signalling on remote wakeup

Set the ehci->resuming flag for the port we receive a remote
wakeup on so that resume signalling can be completed.

Without this, the root hub timer will not fire again to check
if the resume was completed and there will be a never-ending wait on
on the port.

This effect is only observed if the HUB IRQ IN does not come after we
have initiated the port resume.

Signed-off-by: Roger Quadros <rogerq@ti.com>
Cc: stable <stable@vger.kernel.org>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>