USB: gadget: Add EEM gadget driver

This patch adds a CDC EEM ethernet gadget driver.  CDC EEM is a newer
USB ethernet specification that uses a simpler interface than the older
CDC ECM.  This makes CDC EEM usable by a wider set of USB hardware.
By default the ethernet gadget will still use CDC ECM/Subset, but kernel
configuration and/or a module parameter will allow alternative use of
the CDC EEM protocol.

Changes since last version:
	- Brought in missing RNDIS changes that caused compile error
	- Modified 'sentinel CRC' checking to match EEM host driver

Signed-off-by: Brian Niebuhr <bniebuhr@efjohnson.com>
Cc: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/usb/gadget/f_rndis.c b/drivers/usb/gadget/f_rndis.c
index 424a37c..c9966cc 100644
--- a/drivers/usb/gadget/f_rndis.c
+++ b/drivers/usb/gadget/f_rndis.c
@@ -286,12 +286,17 @@
 
 /*-------------------------------------------------------------------------*/
 
-static struct sk_buff *rndis_add_header(struct sk_buff *skb)
+static struct sk_buff *rndis_add_header(struct gether *port,
+					struct sk_buff *skb)
 {
-	skb = skb_realloc_headroom(skb, sizeof(struct rndis_packet_msg_type));
-	if (skb)
-		rndis_add_hdr(skb);
-	return skb;
+	struct sk_buff *skb2;
+
+	skb2 = skb_realloc_headroom(skb, sizeof(struct rndis_packet_msg_type));
+	if (skb2)
+		rndis_add_hdr(skb2);
+
+	dev_kfree_skb_any(skb);
+	return skb2;
 }
 
 static void rndis_response_available(void *_rndis)