user_data2: improve handling when we return user data ranges

user_data2: improve handling when we return user data ranges

Imagine you have a statement that does:

	return val;

Imagine that val is a parameter and it can be user supplied data but it's
not always.  So either we mark it as user data and we end up with false
positives when it's not or we ignore it and we miss real bugs.

What I've decided to do (this isn't a complete solution) is if we know it's
a parameter because the return states are "s32min-s32max[==$1]" then we can
handle that particular case.

We'll see how well this works out in real life.  It obviously fixes the one
particular bug I was looking at.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>