STM32L5 : remove warning

[Warning] serial_device.c@657,41: comparison of different enumeration types ('PinName' and 'UARTName') [-Wenum-compare]
[Warning] serial_device.c@666,41: comparison of different enumeration types ('PinName' and 'UARTName') [-Wenum-compare]
[Warning] serial_device.c@675,41: comparison of different enumeration types ('PinName' and 'UARTName') [-Wenum-compare]
[Warning] serial_device.c@676,41: comparison of different enumeration types ('PinName' and 'UARTName') [-Wenum-compare]

Author: jeromecoutant

targets/TARGET_STM/TARGET_STM32L5/serial_device.c

@@ -654,7 +654,7 @@ static void _serial_set_flow_control_direct(serial_t *obj, FlowControl type, con
     }
     if (type == FlowControlRTS) {
         // Enable RTS
-        MBED_ASSERT(pinmap->rx_flow_pin != (UARTName)NC);
+        MBED_ASSERT(pinmap->rx_flow_pin != NC);
         obj_s->hw_flow_ctl = UART_HWCONTROL_RTS;
         obj_s->pin_rts = pinmap->rx_flow_pin;
         // Enable the pin for RTS function
@@ -663,7 +663,7 @@ static void _serial_set_flow_control_direct(serial_t *obj, FlowControl type, con
     }
     if (type == FlowControlCTS) {
         // Enable CTS
-        MBED_ASSERT(pinmap->tx_flow_pin != (UARTName)NC);
+        MBED_ASSERT(pinmap->tx_flow_pin != NC);
         obj_s->hw_flow_ctl = UART_HWCONTROL_CTS;
         obj_s->pin_cts = pinmap->tx_flow_pin;
         // Enable the pin for CTS function
@@ -672,8 +672,8 @@ static void _serial_set_flow_control_direct(serial_t *obj, FlowControl type, con
     }
     if (type == FlowControlRTSCTS) {
         // Enable CTS & RTS
-        MBED_ASSERT(pinmap->rx_flow_pin != (UARTName)NC);
-        MBED_ASSERT(pinmap->tx_flow_pin != (UARTName)NC);
+        MBED_ASSERT(pinmap->rx_flow_pin != NC);
+        MBED_ASSERT(pinmap->tx_flow_pin != NC);
         obj_s->hw_flow_ctl = UART_HWCONTROL_RTS_CTS;
         obj_s->pin_rts = pinmap->rx_flow_pin;;
         obj_s->pin_cts = pinmap->tx_flow_pin;;