usb: gadget: start with libcomposite

This patch aims to be simple. It removes #include usbstribgs.c line from each
gadget and creates libcomposite.ko which has only one member, that is
usbstribgs.c.

Acked-by: Michal Nazarewicz <mina86@mina86.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Felipe Balbi <balbi@ti.com>
diff --git a/drivers/usb/gadget/Makefile b/drivers/usb/gadget/Makefile
index d84f923..eadbc86 100644
--- a/drivers/usb/gadget/Makefile
+++ b/drivers/usb/gadget/Makefile
@@ -4,6 +4,8 @@
 ccflags-$(CONFIG_USB_GADGET_DEBUG) := -DDEBUG
 
 obj-$(CONFIG_USB_GADGET)	+= udc-core.o
+obj-$(CONFIG_USB_LIBCOMPOSITE)	+= libcomposite.o
+libcomposite-y			:= usbstring.o
 obj-$(CONFIG_USB_DUMMY_HCD)	+= dummy_hcd.o
 obj-$(CONFIG_USB_NET2272)	+= net2272.o
 obj-$(CONFIG_USB_NET2280)	+= net2280.o