When legacy mode is used, the coredump still fails during linking
because "esp_flash_init_default_chip", "esp_flash_app_init" and
"esp_flash_default_chip " are not compiled and linked.
Instead of using ``if`` macros in callers, these functions are protected
by ``if`` macros in the header, and also not compiled in the sources.
"esp_flash_default_chip" variable is compiled with safe default value.
