This define does not belong to the defines in `sdkconfig_*.h` that are used for the ESP-IDF SDK. It is therefore moved to the corresponding `periph_cpu_*.h` file.
The former FLASH_MODE_{DOUT,DIO,QOUT,QIO} defines are replaced by the corresponding CONFIG_FLASHMODE_{DOUT,DIO,QOUT,QIO} and CONFIG_ESPTOOLPY_FLASHMODE_{DOUT,DIO,QOUT,QIO} as used by the ESP-IDF. This is also needed for the migration of defining flash mode in Kconfig.