USB: ehci-platform: support EHCIs with transaction translator

Some EHCI controllers have a Transaction Translator built into
the root hub. Support this feature in device tree when using
the ehci-platform driver by adding a feature flag for it.

This is needed to get USB working on NXP LPC18xx/43xx platforms.

Signed-off-by: Joachim Eastwood <manabian@gmail.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>