Fix broken bootloader build on systems that default to python3
Fix broken bootloader build on systems that default to python3

binascii.hexlify was returning a byte array, which python would
print with a leading b'. Use decode() method to convert to
string.

[ci skip]

jbush001/NyuziProcessor,jbush001/NyuziProcessor,jbush001/NyuziProcessor,jbush001/NyuziProcessor,jbush001/NyuziProcessor,jbush001/NyuziProcessor