AP_RCProtocol: fix missing-declaration warning in example

libraries/AP_RCProtocol/examples/RCProtocolDecoder/RCProtocolDecoder.cpp

@@ -20,6 +20,9 @@
 
 const AP_HAL::HAL& hal = AP_HAL::get_HAL();
 
+void setup();
+void loop();
+
 #if CONFIG_HAL_BOARD == HAL_BOARD_LINUX || CONFIG_HAL_BOARD == HAL_BOARD_SITL
 
 #include <AP_RCProtocol/AP_RCProtocol.h>
@@ -34,10 +37,6 @@ const AP_HAL::HAL& hal = AP_HAL::get_HAL();
 #include <string.h>
 #include <errno.h>
 
-void setup();
-void loop();
-
-
 static AP_RCProtocol *rcprot;
 
 // change this to the device being tested.