Remove superfluous JTAG disable code (#6445)

* Remove superfluous JTAG disable code

* 32A has differently named register

* Accidentally some operators

* 32A also has different JTAG pins

* Wrap disable_jtag() in an ifndef

* Document this new define

* Rename the define, it conflicts with a LUFA thing

Also, move the ifndef wrapping to the call in keyboard_setup()

keyboards/hid_liber/matrix.c

@@ -172,10 +172,6 @@ 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();