STM32WB: Fix serial IRQ handling

Check that the RX or TX interrupt is enabled before calling
a registered handler with RxIrq or TxIrq arg.

Author: Filip Jagodzinski

targets/TARGET_STM/TARGET_STM32WB/serial_device.c

@@ -55,12 +55,12 @@ static void uart_irq(UARTName uart_name)
         UART_HandleTypeDef *huart = &uart_handlers[id];
         if (serial_irq_ids[id] != 0) {
             if (__HAL_UART_GET_FLAG(huart, UART_FLAG_TXE) != RESET) {
-                if (__HAL_UART_GET_IT(huart, UART_IT_TXE) != RESET) {
+                if (__HAL_UART_GET_IT(huart, UART_IT_TXE) != RESET && __HAL_UART_GET_IT_SOURCE(huart, UART_IT_TXE)) {
                     irq_handler(serial_irq_ids[id], TxIrq);
                 }
             }
             if (__HAL_UART_GET_FLAG(huart, UART_FLAG_RXNE) != RESET) {
-                if (__HAL_UART_GET_IT(huart, UART_IT_RXNE) != RESET) {
+                if (__HAL_UART_GET_IT(huart, UART_IT_RXNE) != RESET && __HAL_UART_GET_IT_SOURCE(huart, UART_IT_RXNE)) {
                     irq_handler(serial_irq_ids[id], RxIrq);
                     /* Flag has been cleared when reading the content */
                 }