AP_HAL_Linux: add discard_input method on UARTDriver

libraries/AP_HAL_Linux/UARTDriver.cpp

@@ -293,6 +293,15 @@ int16_t UARTDriver::read()
     return byte;
 }
 
+bool UARTDriver::discard_input()
+{
+    if (!_initialised) {
+        return false;
+    }
+    _readbuf.empty();
+    return true;
+}
+
 /* Linux implementations of Print virtual methods */
 size_t UARTDriver::write(uint8_t c)
 {

libraries/AP_HAL_Linux/UARTDriver.h

@@ -31,6 +31,8 @@ public:
     uint32_t txspace() override;
     int16_t read() override;
 
+    bool discard_input() override;
+
     /* Linux implementations of Print virtual methods */
     size_t write(uint8_t c) override;
     size_t write(const uint8_t *buffer, size_t size) override;