AP_HAL: fixed example build on ChibiOS

libraries/AP_HAL/examples/AnalogIn/AnalogIn.cpp

@@ -5,25 +5,25 @@ void loop();
 
 const AP_HAL::HAL& hal = AP_HAL::get_HAL();
 
-AP_HAL::AnalogSource* ch;
+AP_HAL::AnalogSource* chan;
 
 void setup(void) {
     hal.console->printf("Starting AP_HAL::AnalogIn test\r\n");
-    ch = hal.analogin->channel(0);
+    chan = hal.analogin->channel(0);
 }
 
 static int8_t pin;
 
 void loop(void)
 {
-    float v  = ch->voltage_average();
+    float v  = chan->voltage_average();
     if (pin == 0) {
         hal.console->printf("\n");
     }
     hal.console->printf("[%u %.3f] ",
               (unsigned)pin, (double)v);
     pin = (pin+1) % 16;
-    ch->set_pin(pin);
+    chan->set_pin(pin);
     hal.scheduler->delay(100);
 }