You'd just have to edit the snippet for yourself.
It's located in snippets/cc-mode/for
.
Here's how mine looks like:
# -*- mode: snippet -*-
#name : for (...; ...; ...) { ... }
# --
for (unsigned int ${1:i}=0; $1<${2:N}; ++$1)$0
I insert the braces separately with a function from here, since sometimes you need braces and sometimes not.