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/sx60/matrix.c

@@ -113,13 +113,6 @@ uint8_t matrix_cols(void) {
 }
 
 void matrix_init(void) {
-
-    /* To use PORTF disable JTAG with writing JTD bit twice within four cycles. */
-    #if  (defined(__AVR_AT90USB1286__) || defined(__AVR_AT90USB1287__) || defined(__AVR_ATmega32U4__))
-        MCUCR |= _BV(JTD);
-        MCUCR |= _BV(JTD);
-    #endif
-
     mcp23018_status = true;
 
     /* initialize row and col */