AP_HAL_Empty: do not use ch as its used by ChibiOS globally

libraries/AP_HAL_Empty/RCInput.cpp

@@ -16,8 +16,8 @@ uint8_t RCInput::num_channels() {
     return 0;
 }
 
-uint16_t RCInput::read(uint8_t ch) {
-    if (ch == 2) return 900; /* throttle should be low, for safety */
+uint16_t RCInput::read(uint8_t chan) {
+    if (chan == 2) return 900; /* throttle should be low, for safety */
     else return 1500;
 }
 

libraries/AP_HAL_Empty/RCOutput.cpp

@@ -7,20 +7,20 @@ void RCOutput::init() {}
 
 void RCOutput::set_freq(uint32_t chmask, uint16_t freq_hz) {}
 
-uint16_t RCOutput::get_freq(uint8_t ch) {
+uint16_t RCOutput::get_freq(uint8_t chan) {
     return 50;
 }
 
-void RCOutput::enable_ch(uint8_t ch)
+void RCOutput::enable_ch(uint8_t chan)
 {}
 
-void RCOutput::disable_ch(uint8_t ch)
+void RCOutput::disable_ch(uint8_t chan)
 {}
 
-void RCOutput::write(uint8_t ch, uint16_t period_us)
+void RCOutput::write(uint8_t chan, uint16_t period_us)
 {}
 
-uint16_t RCOutput::read(uint8_t ch) {
+uint16_t RCOutput::read(uint8_t chan) {
     return 900;
 }