analog-avr.c: no need to re-initialise adc_counter.

After firmware startup it's always in a valid range, even in the
unlikely case analog_init() is called twice.

This saves 4 bytes binary size without drawback.

analog-avr.c

@@ -9,7 +9,7 @@
 #include	"memory_barrier.h"
 
 
-static uint8_t adc_counter;
+static uint8_t adc_counter = 0;
 static volatile uint16_t BSS adc_result[NUM_TEMP_SENSORS];
 
 //! Configure all registers, start interrupt loop
@@ -32,8 +32,6 @@ void analog_init() {
 			ADCSRB = 0;
 		#endif
 
-		adc_counter = 0;
-
 		// clear analog inputs in the data direction register(s)
 		AIO0_DDR &= ~analog_mask;
 		#ifdef	AIO8_DDR