feat: Add support for SpaceMouse mod (6D input knob) (#1853)

Use `-DSPACEMOUSE=YES` CMake option to activate on Horus color targets.
Co-authored-by: Niel Horne (elecpower), Raphael Coeffic (raphaelcoeffic) and Peter Feerick (pfeerick).

radio/src/serial.cpp

@@ -212,6 +212,11 @@ static void serialSetCallBacks(int mode, void* ctx, const etx_serial_port_t* por
     gpsSetSerialDriver(ctx, drv);
     break;
 #endif
+#if defined(SPACEMOUSE)
+  case UART_MODE_SPACEMOUSE:
+    spacemouseSetSerialDriver(ctx, drv);
+    break;
+#endif
 #endif
   }
 }
@@ -267,6 +272,13 @@ static void serialSetupPort(int mode, etx_serial_init& params)
     params.rx_enable = true;
     break;
 #endif
+
+#if defined(SPACEMOUSE)
+  case UART_MODE_SPACEMOUSE:
+    params.baudrate = SPACEMOUSE_BAUDRATE;
+    params.rx_enable = true;
+    break;
+#endif
 #endif
   }
 }