ports/mega: Switch clock to timer 2

This follows the other atmega users which want to allow timer 2 to be
used for the tone operation.

Signed-off-by: Keith Packard <keithp@keithp.com>

ports/mega/snek-mega.c

@@ -13,6 +13,7 @@
  */
 
 #include "snek.h"
+#include "snek-io.h"
 
 #define NUM_PIN	70
 #define A0	54
@@ -51,13 +52,10 @@ port_init(void)
 
 	/* / 64 */
 	TCCR0B = ((0 << CS02) |
-		  (1 << CS01) |
+		  (0 << CS01) |
 		  (1 << CS00) |
 		  (0 << WGM02));
 
-	/* enable interrupt */
-	TIMSK0 = (1 << TOIE0);
-
 	/* Timer 1 */
 	TCCR1B = ((0 << CS12) |
 		  (1 << CS11) |
@@ -77,6 +75,9 @@ port_init(void)
 
 	TCCR2A = ((1 << WGM20));
 
+	/* enable interrupt */
+	TIMSK2 = (1 << TOIE2);
+
 	/* Timer 3 */
 	TCCR3B = ((0 << CS12) |
 		  (1 << CS11) |