Hi Massimiliano Cialdi
From KSDK 2.x, we merged all original KSDK 1.3 flash source filess in fsl_flash.c
For example, for Frdm-K64f, this file is under the below folder
SDK_2.2_FRDM-K64F\devices\MK64F12\drivers\fsl_flash.c
I guess below two flash APIs are what your are looking for.
FLASH_SwapControl()
FLASH_Swap
Regards
Daniel