usb-gadget: Initial merge of target module for UASP + BOT

This fabric uses the target framework to provide a usb gadget
device.  This gadget supports the USB Attached SCSI Protocol (UASP)
and Bulk Only Transfers (BOT or BBB). BOT is the primary interface,
UAS is the alternative interface.

It has been tested with dummy_hcd on HS and SS. On SS USB3 are
supported. I also took my omap device and tried it there against
WindowsXP.  UAS implements basic command passing (i.e. read/write
requests) and TASK MANAGEMENT functions are missing.

I had to add a little of error recovery to BOT because Windows was
issuing some strange commands and it does not complain after the
gadget responded with CSW.status=1.

(nab: Move to drivers/usb/gadget as per Sebastian to address legacy
      limitations for built-in gadget code)

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Acked-by: Felipe Balbi <balbi@ti.com>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Greg KH <gregkh@linuxfoundation.org>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

Author: Sebastian Andrzej Siewior

drivers/usb/gadget/Kconfig

@@ -798,6 +798,16 @@ config USB_MASS_STORAGE
 	  Say "y" to link the driver statically, or "m" to build
 	  a dynamically linked module called "g_mass_storage".
 
+config USB_GADGET_TARGET
+	tristate "USB Gadget Target Fabric Module"
+	depends on TARGET_CORE
+	help
+	  This fabric is an USB gadget. Two USB protocols are supported that is
+	  BBB or BOT (Bulk Only Transport) and UAS (USB Attached SCSI). BOT is
+	  advertised on alternative interface 0 (primary) and UAS is on
+	  alternative interface 1. Both protocols can work on USB2.0 and USB3.0.
+	  UAS utilizes the USB 3.0 feature called streams support.
+
 config USB_G_SERIAL
 	tristate "Serial Gadget (with CDC ACM and CDC OBEX support)"
 	help

drivers/usb/gadget/Makefile

@@ -52,6 +52,7 @@ g_nokia-y			:= nokia.o
 g_webcam-y			:= webcam.o
 g_ncm-y				:= ncm.o
 g_acm_ms-y			:= acm_ms.o
+g_tcm_usb_gadget-y		:= tcm_usb_gadget.o
 
 obj-$(CONFIG_USB_ZERO)		+= g_zero.o
 obj-$(CONFIG_USB_AUDIO)		+= g_audio.o
@@ -71,3 +72,4 @@ obj-$(CONFIG_USB_G_NOKIA)	+= g_nokia.o
 obj-$(CONFIG_USB_G_WEBCAM)	+= g_webcam.o
 obj-$(CONFIG_USB_G_NCM)		+= g_ncm.o
 obj-$(CONFIG_USB_G_ACM_MS)	+= g_acm_ms.o
+obj-$(CONFIG_USB_GADGET_TARGET)	+= tcm_usb_gadget.o