Add SeeedStudio Xiao mg24

[darkxst]

Add support for SeedStudio XIAO MG24 devkit. This device requires to flash bootloader first.

You will need to use openocd to flash bootloader

openocd -s scripts/ -f interface/cmsis-dap.cfg -f target/efm32s2_g23.cfg -c "flash bank bank0 efm32s2 0x08000000 0x6000 0 0 0 efm32s2.cpu; init; reset_config srst_nogate; program  ../xiao_mg24_bootloader_2.5.2_BL_PC00.hex; reset; exit"

Upstream openocd doesnt have support for efm32s2 target so I used the packages provided for unbricking device:
https://wiki.seeedstudio.com/xiao_mg24_getting_started/#unbricking

After that you can just use universal-silabs-flasher to flash Zigbee firmware

universal_silabs_flasher.flasher INFO Detected ApplicationType.EZSP, version '8.0.2.0 build 397' (8.0.2.0.397) at 115200 baudrate (bootloader baudrate None)