AP_Params: fix seg fault in debug function

otherwise at start, when loading paramter is could fail at AP_Param.cpp:611, Debug("scan past end of eeprom")"

libraries/AP_Param/AP_Param.cpp

@@ -38,7 +38,7 @@ extern const AP_HAL::HAL &hal;
 #define ENABLE_DEBUG 1
 
 #if ENABLE_DEBUG
- # define Debug(fmt, args ...)  do {hal.console->printf("%s:%d: " fmt "\n", __FUNCTION__, __LINE__, ## args); } while(0)
+ # define Debug(fmt, args ...)  do {::printf("%s:%d: " fmt "\n", __FUNCTION__, __LINE__, ## args); } while(0)
 #else
  # define Debug(fmt, args ...)
 #endif