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()

docs/faq_debug.md

@@ -184,22 +184,15 @@ Pressing any key during sleep should wake host.
 
 Arduino Leonardo and micro have **ATMega32U4** and can be used for TMK, though Arduino bootloader may be a problem.
 
+## Enabling JTAG
 
-## Using PF4-7 Pins of USB AVR?
-You need to set JTD bit of MCUCR yourself to use PF4-7 as GPIO. Those pins are configured to serve JTAG function by default. MCUs like ATMega*U* or AT90USB* are affected with this.
+By default, the JTAG debugging interface is disabled as soon as the keyboard starts up. JTAG-capable MCUs come from the factory with the `JTAGEN` fuse set, and it takes over certain pins of the MCU that the board may be using for the switch matrix, LEDs, etc.
 
-If you are using Teensy this isn't needed. Teensy is shipped with JTAGEN fuse bit unprogrammed to disable the function.
+If you would like to keep JTAG enabled, just add the following to your `config.h`:
 
-See this code.
+```c
+#define NO_JTAG_DISABLE
 ```
-    // JTAG disable for PORT F. write JTD bit twice within four cycles.
-    MCUCR |= (1<<JTD);
-    MCUCR |= (1<<JTD);
-```
-https://github.com/tmk/tmk_keyboard/blob/master/keyboard/hbkb/matrix.c#L67
-
-And read **26.5.1 MCU Control Register – MCUCR** of ATMega32U4 datasheet.
-
 
 ## Adding LED Indicators of Lock Keys
 You need your own LED indicators for CapsLock, ScrollLock and NumLock? See this post.

docs/zh-cn/faq_debug.md

@@ -173,23 +173,6 @@ EXTRAKEY_ENABLE = yes          # 音频控制和系统控制
 
 Arduino Leonardo和micro使用**ATMega32U4**，该芯片TMK可用，但Arduino的bootloader会导致问题。
 
-
-## 在USB AVR使用PF4-7针脚?
-你要置位MCUCR寄存器JTD位来将PF4-7设置为GPIO。这些针脚默认是JTAG功能。 像ATMega*U* or AT90USB*这样的MCU会受影响。
-
-如果是用Teensy的话就不需要了。Tennsy自带JTAGEN位未编程来失能该功能。
-<!--翻译问题：上句可能有错，原文为：Teensy is shipped with JTAGEN fuse bit unprogrammed to disable the function. -->
-代码如下。
-```
-    // F接口JTAG失能。在四个周期内写入两次JTD位。
-    MCUCR |= (1<<JTD);
-    MCUCR |= (1<<JTD);
-```
-https://github.com/tmk/tmk_keyboard/blob/master/keyboard/hbkb/matrix.c#L67
-
-阅读ATMega32U4的datasheet中的**26.5.1 MCU Control Register – MCUCR**。
-
-
 ## 为锁定键添加指示灯
 你要自制CapsLock, ScrollLock 和 NumLock指示灯？见下文。