usb: imx: implement support for limiting host to full speed ...

This is needed when host is known to not work properly in high speed
mode.

In linux, chipidea driver supports 'maximum-speed' device tree property.
When that is set to "full-speed", driver sets PFSC bit in PORTSC
register, which disallows use of high speed mode.

This patch implements same support for barebox.

Important technical detail is that PFSC bit is cleared by port reset,
thus setting it has to be done in ehci->init() callback which is called
after ehci_reset().

Signed-off-by: Nikita Yushchenko <nikita.yoush@cogentembedded.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

USB: gadget: Update to 3.15 ...

This updates the USB Gadget stack to Linux-3.15.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

Conflicts:
	drivers/usb/core/Makefile

Documentation: remove doxygen documentation ...

The doxygen documentation is long outdated. Remove it. It will
be replaced with sphinx based documentation later.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

documentation updates ...

Signed-off-by: Juergen Beisert <jbe@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

Add USB device support ...

This patch adds support for USB devices. It uses
the Linux Kernel gadget API. Along with this patch
comes driver support for the Freescale (arc) USB OTG
Core and USB Device Firmware Update (DFU)
The serial gadget support is not working at the moment.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>