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 --cc drivers/usb/gadget/Kconfig
Simple merge

diff --cc drivers/usb/gadget/Makefile
Simple merge

diff --cc drivers/usb/gadget/acm_ms.c
Simple merge

diff --cc drivers/usb/gadget/audio.c
Simple merge

diff --cc drivers/usb/gadget/cdc2.c
Simple merge

diff --cc drivers/usb/gadget/ether.c
Simple merge

diff --cc drivers/usb/gadget/file_storage.c
Simple merge

diff --cc drivers/usb/gadget/g_ffs.c
Simple merge

diff --cc drivers/usb/gadget/gmidi.c
Simple merge

diff --cc drivers/usb/gadget/hid.c
Simple merge

diff --cc drivers/usb/gadget/mass_storage.c
Simple merge

diff --cc drivers/usb/gadget/multi.c
Simple merge

diff --cc drivers/usb/gadget/ncm.c
Simple merge

diff --cc drivers/usb/gadget/nokia.c
Simple merge

diff --cc drivers/usb/gadget/printer.c
Simple merge

diff --cc drivers/usb/gadget/serial.c
Simple merge

diff --cc drivers/usb/gadget/tcm_usb_gadget.c
Simple merge

diff --cc drivers/usb/gadget/usbstring.c
Simple merge

diff --cc drivers/usb/gadget/webcam.c
Simple merge

diff --cc drivers/usb/gadget/zero.c
Simple merge