random: make it possible to enable debugging without rebuild
The module parameter that turns debugging mode (which basically means
printing a few extra lines during runtime) is in '#if 0' block. Forcing
everyone who would like to see how entropy is behaving on his system to
rebuild seems to be a little bit too harsh.
If we were concerned about speed, we could potentially turn 'debug' into a
static key, but I don't think it's necessary.
Drop the '#if 0' block to allow using the 'debug' parameter without
rebuilding.