USB bus drivers: Add missing iterator increments.

Should fix boot hang regressions introduced in hrev55455
in the fix for #17275.

src/add-ons/kernel/busses/usb/ehci.cpp

@@ -1558,6 +1558,8 @@ EHCI::AddPendingTransfer(Transfer *transfer, ehci_qh *queueHead,
 			delete data;
 			return B_DEV_RESOURCE_CONFLICT;
 		}
+
+		it = it->link;
 	}
 
 	if (fLastTransfer)

src/add-ons/kernel/busses/usb/ohci.cpp

@@ -1460,6 +1460,8 @@ OHCI::_SubmitTransfer(Transfer *transfer)
 			_FreeDescriptorChain(firstDescriptor);
 			return B_DEV_RESOURCE_CONFLICT;
 		}
+
+		it = it->link;
 	}
 
 	result = _AddPendingTransfer(transfer, endpoint, firstDescriptor,

src/add-ons/kernel/busses/usb/uhci.cpp

@@ -1076,6 +1076,8 @@ UHCI::AddPendingTransfer(Transfer *transfer, Queue *queue,
 			delete data;
 			return B_DEV_RESOURCE_CONFLICT;
 		}
+
+		it = it->link;
 	}
 
 	if (fLastTransfer)