Declare LoopCounterSymbols nonnegative

This removed some checks like `ctr1 <= 0` from my kernels
10 jobs for LoopCounterSymbols-nonnegative in 3 minutes and 34 seconds (queued for 2 seconds)
latest
Name Stage Failure
failed
minimal-sympy-master Test
    for term in self.args]
File "/opt/conda/lib/python3.7/site-packages/sympy/core/basic.py", line 1691, in doit
for term in self.args]
File "/opt/conda/lib/python3.7/site-packages/sympy/core/basic.py", line 1691, in <listcomp>
for term in self.args]
File "/opt/conda/lib/python3.7/site-packages/sympy/core/basic.py", line 1692, in doit
return self.func(*terms)
TypeError: __init__() missing 1 required positional argument: 'dtype'
ERROR: Job failed: exit code 1