Wrong CRC calculation in upgrade_crc_check

[hammer-dp-ua]

Please rollback a change made in 10.25.2016 08:27:15 by SeregaKai.
abs function was placed not just by mistake. Looks like it converts "unsigned int" to "int" inside itself and then really changes bitwise representation if int result is negative.

[borro0]

I agree on this. The gen_appbin.py used to generate the crc in the first place, also uses abs.