qcacmn: WAR for invalid length buffers in wbm rx error path

WAR for wrong length in first msdu in wbm rx error path while
handling scatter gather buffers. Get the msdu length from the
last buffer instead.

Change-Id: I869391ef5ca7005dce972013679c2143be836ecb

dp/wifi3.0/dp_rx.c

@@ -1529,8 +1529,10 @@ qdf_nbuf_t dp_rx_sg_create(struct dp_soc *soc, qdf_nbuf_t nbuf)
 			next = nbuf->next;
 			nbuf->next = NULL;
 			break;
+		} else if (qdf_nbuf_is_rx_chfrag_end(nbuf)) {
+			dp_err("Invalid packet length\n");
+			qdf_assert_always(0);
 		}
-
 		nbuf = nbuf->next;
 	} while (!last_nbuf);