ndis: Add debug support to disable RNDIS Multipacket Feature

This change adds module param which allows to disable RNDIS
Multi-packet Feature (Aggregation support in Downlink path)
as this feature is enabled by default.

To disable use this param before moving to RNDIS Composition:
echo 1 > /sys/module/g_android/parameters/rndis_multipacket_dl_disable

Also counts errors as Rx errors if received RNDIS packets are
not following RNDIS message format as those packets are being
discarded.

Change-Id: I764430da78f2204af92e14bb279c11b24c7e4c67
Signed-off-by: Mayank Rana <mrana@codeaurora.org>
diff --git a/drivers/usb/gadget/function/u_ether.c b/drivers/usb/gadget/function/u_ether.c
index 12e3425..0ade386 100644
--- a/drivers/usb/gadget/function/u_ether.c
+++ b/drivers/usb/gadget/function/u_ether.c
@@ -288,6 +288,10 @@
 				status = dev->unwrap(dev->port_usb,
 							skb,
 							&dev->rx_frames);
+				if (status == -EINVAL)
+					dev->net->stats.rx_errors++;
+				else if (status == -EOVERFLOW)
+					dev->net->stats.rx_over_errors++;
 			} else {
 				dev_kfree_skb_any(skb);
 				status = -ENOTCONN;