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

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

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

The file is now compiled into a separate usb_f_eem.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/ether.c b/drivers/usb/gadget/ether.c
index f4d46d7..397609d 100644
--- a/drivers/usb/gadget/ether.c
+++ b/drivers/usb/gadget/ether.c
@@ -108,6 +108,8 @@
 #include "f_rndis.c"
 #include "rndis.h"
 #endif
+
+#define USB_FEEM_INCLUDED
 #include "f_eem.c"
 
 /*-------------------------------------------------------------------------*/