This patch adds the USB Mass Storage Gadget to u-boot
New command called "ums" is implemented to provide access
to on-device embedded persistent memory.
USB Mass Storage is supposed to work on top of the USB
Gadget framework
Signed-off-by: Lukasz Majewski <l.majewski@samsung.com> Signed-off-by: Piotr Wilczek <p.wilczek@samsung.com> Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com> CC: Marek Vasut <marek.vasut@gmail.com>