BACKPORT: usb: gadget: add tracepoints to the gadget API

This new set of tracepoints will help all gadget
drivers and UDC drivers when problem appears. Note
that, in order to be able to add tracepoints to
udc-core.c we had to rename that to core.c and
statically link it with trace.c to form
udc-core.o. This is to make sure that module name
stays the same.

Change-Id: I23eb801151a75629a8a2f6e7d9203f58281ed3d2
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>
Signed-off-by: William Wu <william.wu@rock-chips.com>
(cherry picked from commit 5e42d710a108c23c104e083900d4ba9398e418b0)

Author: wuliangfeng

drivers/usb/gadget/udc/Makefile

@@ -1,3 +1,8 @@
+# define_trace.h needs to know how to find our header
+CFLAGS_trace.o			:= -I$(src)
+
+udc-core-y			:= core.o trace.o
+
 #
 # USB peripheral controller drivers
 #