usb:gadget: USB Mass Storage Gadget support

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>
diff --git a/common/Makefile b/common/Makefile
index 08af1a8..1abf4ea 100644
--- a/common/Makefile
+++ b/common/Makefile
@@ -179,6 +179,7 @@
 COBJS-y += usb.o usb_hub.o
 COBJS-$(CONFIG_USB_STORAGE) += usb_storage.o
 endif
+COBJS-$(CONFIG_CMD_USB_MASS_STORAGE) += cmd_usb_mass_storage.o
 COBJS-$(CONFIG_CMD_XIMG) += cmd_ximg.o
 COBJS-$(CONFIG_YAFFS2) += cmd_yaffs2.o
 COBJS-$(CONFIG_CMD_SPL) += cmd_spl.o