TempScopInfo: Microoptimize constant conditions

Use 0 >= 1 instead of 0 != 0 to represent 'false'. This might be slightly more
efficient as isl may create a union of sets for 0 != 0, whereas this is never
needed for the expression 0 >= 1.

Contributed-by: Alexandre Isoard <alexandre.isoard@gmail.com>
llvm-svn: 190384