Restore some openocd information which I occassionally need.
This is a partial revert of:
```
commit 58a5e0744b
Author: Abdelatif Guettouche <abdelatif.guettouche@espressif.com>
Date: Mon Jul 26 21:43:42 2021 +0200
Documentation/esp32: Remove the rest of the OpenOCD text.
This information there is outdated and some of its content should be in
the board documentation and not the chip.
Signed-off-by: Abdelatif Guettouche <abdelatif.guettouche@espressif.com>
```
Summary:
- The CONFIG_SMP_IDLETHREAD_STACKSIZE was introduced to optimize
the idle stack size for other than CPU0
- However, there are no big differences between the idle stacks.
- This commit removes the config to simplify the kernel code
Impact:
- All SMP configurations
Testing:
- Tested with ostest with the following configs
- spresense:smp, spresense:rndis_smp
- esp32-devkitc:smp (QEMU), maix-bit:smp (QEMU)
- sabre-6quad:smp (QEMU), sabre-6quad:netnsh_smp (QEMU)
- raspberrypi-pico:smp, sim:smp (x86_64)
Signed-off-by: Masayuki Ishikawa <asayuki.Ishikawa@jp.sony.com>
