Copter: remove DigitalReadFast

With APHal all reads are fast

ArduCopter/compat.pde

@@ -30,11 +30,6 @@ void digitalWrite(uint8_t pin, uint8_t out)
     hal.gpio->write(pin,out);
 }
 
-uint8_t digitalReadFast(uint8_t pin)
-{
-    return hal.gpio->read(pin);
-}
-
 uint8_t digitalRead(uint8_t pin)
 {
     return hal.gpio->read(pin);

ArduCopter/system.pde

@@ -82,7 +82,7 @@ static void init_ardupilot()
     // USB_MUX_PIN
     pinMode(USB_MUX_PIN, INPUT);
 
-    ap_system.usb_connected = !digitalReadFast(USB_MUX_PIN);
+    ap_system.usb_connected = !digitalRead(USB_MUX_PIN);
     if (!ap_system.usb_connected) {
         // USB is not connected, this means UART0 may be a Xbee, with
         // its darned bricking problem. We can't write to it for at
@@ -534,7 +534,7 @@ static uint32_t map_baudrate(int8_t rate, uint32_t default_baud)
 #if USB_MUX_PIN > 0
 static void check_usb_mux(void)
 {
-    bool usb_check = !digitalReadFast(USB_MUX_PIN);
+    bool usb_check = !digitalRead(USB_MUX_PIN);
     if (usb_check == ap_system.usb_connected) {
         return;
     }