USB: Add EHCI support for MX27 and MX31 based boards

The Freescale MX27 and MX31 SoCs have a EHCI controller onboard.
The controller is capable of USB on the go. This patch adds
a driver to support all three of them.

Users have to pass details about serial interface configuration in the
platform data.

The USB OTG core used here is the ARC core, so the driver should
be renamed and probably be merged with ehci-fsl.c eventually.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Daniel Mack <daniel@caiaq.de>
Cc: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>