usb: gadget: libcomposite: move composite.c into libcomposite

This moves composite.c into libcomposite and updates all gadgets.
Finally!

Acked-by: Michal Nazarewicz <mina86@mina86.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Felipe Balbi <balbi@ti.com>

drivers/usb/gadget/acm_ms.c

@@ -15,6 +15,7 @@
  */
 
 #include <linux/kernel.h>
+#include <linux/module.h>
 
 #include "u_serial.h"
 
@@ -40,7 +41,6 @@
  * a "gcc --combine ... part1.c part2.c part3.c ... " build would.
  */
 
-#include "composite.c"
 #include "u_serial.c"
 #include "f_acm.c"
 #include "f_mass_storage.c"