Disable JTAG function for hid_liber to use PORTF.

keyboard/hid_liber/matrix.c

@@ -137,6 +137,10 @@ uint8_t matrix_cols(void)
 
 void matrix_init(void)
 {
+    // To use PORTF disable JTAG with writing JTD bit twice within four cycles.
+    MCUCR |= (1<<JTD);
+    MCUCR |= (1<<JTD);
+
     // initialize row and col
     setup_io_pins();
     setup_leds();