Fix delete delete hang on serial ports

Found the issue where it was freeing transfers from the follow up list, that were also on the QH list which also tried to free it again.

Fix was in the first free list, it checks to see if the item is also in the qh list and does not free it then.

ehci.cpp

@@ -1252,12 +1252,38 @@ void USBHost::delete_Pipe(Pipe_t *pipe)
 			// TODO: does this write interfere UPI & UAI (bits 18 & 19) ??
 		}
 		// find & free all the transfers which completed
+		println("  Free transfers");
 		Transfer_t *t = async_followup_first;
+#if 0
+		if (t) {
+			println("  (Look at QH list first)");
+			Transfer_t *tr = (Transfer_t *)(pipe->qh.next);
+			while ((uint32_t)tr & 0xFFFFFFE0) {
+				println("    $ ", (uint32_t)tr);
+				tr  = (Transfer_t *)(tr->qtd.next);
+			}
+		}
+#endif		
 		while (t) {
+			print("    * ", (uint32_t)t);
 			Transfer_t *next = t->next_followup;
 			if (t->pipe == pipe) {
+				print(" * remove");
 				remove_from_async_followup_list(t);
-				free_Transfer(t);
+
+				// Only free if not in QH list
+				Transfer_t *tr = (Transfer_t *)(pipe->qh.next);
+				while (((uint32_t)tr & 0xFFFFFFE0) && (tr != t)){
+					tr  = (Transfer_t *)(tr->qtd.next);
+				}
+				if (tr == t) {
+					println(" * defer free until QH");
+				} else {
+					println(" * free");
+					free_Transfer(t);  // The later code should actually free it...
+				}
+			} else {
+				println("");
 			}
 			t = next;
 		}
@@ -1300,14 +1326,17 @@ void USBHost::delete_Pipe(Pipe_t *pipe)
 	// TODO: do we need to look at pipe->qh.current ??
 	//
 	// free all the transfers still attached to the QH
+	println("  Free transfers attached to QH");
 	Transfer_t *tr = (Transfer_t *)(pipe->qh.next);
 	while ((uint32_t)tr & 0xFFFFFFE0) {
+		println("    * ", (uint32_t)tr);
 		Transfer_t *next = (Transfer_t *)(tr->qtd.next);
 		free_Transfer(tr);
 		tr = next;
 	}
 	// hopefully we found everything...
 	free_Pipe(pipe);
+	println("* Delete Pipe completed");
 }