OPEN BLT for STM32F407VG-DISC1

This implementation uses ARMCM4_STM32F4_Olimex_STM32P405_CubeIDE as basis to build custom open bootloader for STM32F407VG-DISC1 Please find changes made below

1. Seed and key is enabled
2. Seed and key algorithm is slightly changed just for testing purposes

for more information one can refer to Feaser GitHub Repositoty