kconfig/ devicetree contents

I use `rev5`, `rev6`, etc. for the different revisions of the PCB containing an nrf52840.
```
   boards
  └  arm
    │  rev5
    │ │ * Kconfig.board
    │ │ * Kconfig.defconfig
    │ │  board.cmake
    │ │  board.yml <-- not needed for VSCode, yet needed for standalone `west`, why??
    │ │ * rev5.dts
    │ │  rev5.yaml
    │ └ * rev5_defconfig
    │  rev6
    │  rev7
    └  rev8
```


board.yml:
- NOTE: `VSCode + west` does not require this file, but without this file I get the following error when compiling with standalone `west`: https://pastebin.com/gJSTZbpt
```
board: # TODO: dont know if/why we need this for west from CLI
  name: rev5
  socs:
    - name: nrf52840
```


KConfig.board:
```
config BOARD_REV5
    bool "rev5 board"
    # am i supposed to depend on this or select it? I've seen both in examples!
    depends on SOC_NRF52840_QFAA
    # select SOC_NRF52840_QFAA
```


Kconfig.defconfig:
```
if BOARD_REV5
config BOARD
    default "rev5"

config BT_CTLR
   default BT

endif
```

rev5.dts:
```
/dts-v1/;
#include <nordic/nrf52840_qfaa.dtsi>
/ {
    model = "rev5";
    compatible = "vendor,rev5";

    chosen {
        zephyr,sram = &sram0;
        zephyr,flash = &flash0;
        zephyr,code-partition = &slot0_partition;
    };

    ...
    various leds, buttons, ...
};
...
```

rev5.yaml:
```
identifier: rev5
name: rev5
type: mcu
arch: arm
ram: 256
flash: 1024
toolchain:
  - zephyr
  - gnuarmemb
  - xtools
```