usb: gadget: f_ncm: convert to new function interface with backward compatibility

Converting ncm to the new function interface requires converting
the USB ncm's function code and its users.

This patch converts the f_ncm.c to the new function interface.

The file is now compiled into a separate usb_f_ncm.ko module.

The old function interface is provided by means of a preprocessor
conditional directives. After all users are converted, the old interface
can be removed.

Signed-off-by: Andrzej Pietrasiewicz <andrzej.p@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>
diff --git a/drivers/usb/gadget/Makefile b/drivers/usb/gadget/Makefile
index 7a0463e..34b117e 100644
--- a/drivers/usb/gadget/Makefile
+++ b/drivers/usb/gadget/Makefile
@@ -48,6 +48,8 @@
 obj-$(CONFIG_USB_U_ETHER)	+= u_ether.o
 u_rndis-y			:= rndis.o
 obj-$(CONFIG_USB_U_RNDIS)	+= u_rndis.o
+usb_f_ncm-y			:= f_ncm.o
+obj-$(CONFIG_USB_F_NCM)		+= usb_f_ncm.o
 
 #
 # USB gadget drivers