[llvm][Analysis] Silence warning when building with MSVC

When building an assert-enabled target, silence the following:
```
C:\git\llvm-project\llvm\include\llvm/Analysis/DependenceAnalysis.h(290): warning C4018: '<=': signed/unsigned mismatch
```

Author: aganea

llvm/include/llvm/Analysis/DependenceAnalysis.h

@@ -287,7 +287,8 @@ class LLVM_ABI FullDependence final : public Dependence {
       assert(0 < Level && Level <= Levels && "Level out of range");
       return DV[Level - 1];
     } else {
-      assert(Levels < Level && Level <= Levels + SameSDLevels &&
+      assert(Levels < Level &&
+             Level <= static_cast<unsigned>(Levels) + SameSDLevels &&
              "isSameSD level out of range");
       return DVSameSD[Level - Levels - 1];
     }

llvm/lib/Analysis/DependenceAnalysis.cpp

@@ -389,7 +389,8 @@ bool FullDependence::isSplitable(unsigned Level, bool isSameSD) const {
 // performed across two separate loop nests that have the Same iteration space
 // and Depth.
 bool FullDependence::inSameSDLoops(unsigned Level) const {
-  assert(0 < Level && Level <= Levels + SameSDLevels && "Level out of range");
+  assert(0 < Level && Level <= static_cast<unsigned>(Levels) + SameSDLevels &&
+         "Level out of range");
   return Level > Levels;
 }