Flashing yaota8266.bin to clean flash leads to bootloop

[pfalcon]

This is mostly a reminder that with SDK2.0, any app (including ota-server) will go into bootloop, if esp_init_data_default.bin is not flashed.

Dunno how to fix this, if at all. The best solution would be to make boot8266 to write the default data there, but that means it will need to detect flash size (in a way compatible with SDK).