Various USB related patches

Various USB related patches
- Add support for mpc8xx USB device.
- Add support for Common Device Class - Abstract Control Model USB console.
- Add support for flow control in USB slave devices.
- Add support for switching between gserial and cdc_acm using environment.
- Minor changes to usbdcore_omap1510.c usbdcore_omap1510.h
- Update usbcore slightly to ease host enumeration.
- Fix non-portable endian problems in usbdcore and usbdcore_ep0.
- Add AdderUSB_config as a defconfig to enable usage of the USB console
  by default with the Adder87x U-Boot port.
Patches by Bryan O'Donoghue <bodonoghue@codehermit.ie>, 29 May 2006