usb3-drd: import header file

* Import header file for usv3-drd
* Used by board-smdk5250 and board-exshields

Signed-off-by: Adrian Alonso <aalonso@htdevices.com>
usb-switch: new header file

* Import usb-switch header file used by
  board-smdk5250 and exshields

Signed-off-by: Adrian Alonso <aalonso@htdevices.com>
board-exshields-usb: new file usb support

* Add usb 2/3 support for exshields board
* based on board-smdk5250-usb board settings

Signed-off-by: Adrian Alonso <aalonso@htdevices.com>
board-exshields: add usb 2/3 support

* Add usb 2/3 support for exshields board
  exynos5_exshields_usb_init

Signed-off-by: Adrian Alonso <aalonso@htdevices.com>
Makefile: add exshield usb build option

* Add exshield board build option

Signed-off-by: Adrian Alonso <aalonso@htdevices.com>