serial: stm32: correct flow control property spelling

"st,hw-flow-ctrl" property is documented in device tree
binding whereas "auto-flow-control" was used in the code.
The driver is now aligned with the binding name
"st,hw-flow-ctrl".
Signed-off-by: Gerald Baeza <gerald.baeza@st.com>
Signed-off-by: Alexandre TORGUE <alexandre.torgue@st.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/stm32-usart.c

@@ -508,7 +508,7 @@ static struct stm32_port *stm32_of_get_stm32_port(struct platform_device *pdev)
 		return NULL;
 
 	stm32_ports[id].hw_flow_control = of_property_read_bool(np,
-							"auto-flow-control");
+							"st,hw-flow-ctrl");
 	stm32_ports[id].port.line = id;
 	return &stm32_ports[id];
 }