If you want to load ST-LINK/V2-1 firmware, you should also modify the compiled bootloader firmware.
At the offset of 0x100, the values must be 0x15 0x3c 0xa5 0x47, like this:
00000100 15 3c a5 47 31 11 00 08 31 11 00 08 31 11 00 08 |.<.G1...1...1...|