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/amj96/matrix.c

@@ -63,9 +63,6 @@ void matrix_init(void)
 #ifdef UART_RGB_ENABLE
     uart_rgb_init();
 #endif
-    // disable JTAG
-    MCUCR = _BV(JTD);
-    MCUCR = _BV(JTD);
 
     // 85 REST
     DDRD |= _BV(PD7);