espressif:esp32: Move app entry point call back to iram_loader_seg region

Entry point call was moved back from main to esp_loader, so it is
called from iram_loader_seg memory region

Signed-off-by: Almir Okato <almir.okato@espressif.com>
(cherry picked from commit c4b30586)
Signed-off-by: Andrzej Puzdrowski <andrzej.puzdrowski@nordicsemi.no>