Fix unused pin PB0 being used in init

This pin is unused and shouldn't be set by the library.

spi.c

@@ -2,10 +2,10 @@
 
 void spi_init(void) {
 	// Set MOSI and SCK, SS/CS output, all others input
-	DDRB = (1<<PB3) | (1<<PB5) | (1<<PB2) | (1<<PB0);
+	DDRB = (1<<PB3) | (1<<PB5) | (1<<PB2);
 	// Enable SPI, Master, set clock rate fck/4, mode 0
 	SPCR = (1<<SPE) | (1<<MSTR);
 
 	// Set SS/CS
-	PORTB |= (1 << PB2) | (1 << PB0);
+	PORTB |= (1 << PB2);
 }