[OpenMP] Fix sign comparison warnings from GCC

[jlpeyton]

Summary

New affinity patch introduced legitimate sign-compare warnings that clang doesn't report but GCC-10 does. This removes the warnings by changing two variables types to unsigned.

[AndreyChurbanov]

LGTM

openmp/runtime/src/kmp_affinity.cpp

while (top_index1 < depth - 1 && top_index2 < depth) {
     kmp_hw_t type1 = types[top_index1];
     kmp_hw_t type2 = types[top_index2];
     if (type1 == KMP_HW_SOCKET && type2 == KMP_HW_CORE) {
       top_index1 = top_index2++;
       continue;
     }
     bool radix1 = true;
     bool all_same = true;
-    int id1 = addrP[0].first.labels[top_index1];
-    int id2 = addrP[0].first.labels[top_index2];
+    unsigned id1 = addrP[0].first.labels[top_index1];
+    unsigned id2 = addrP[0].first.labels[top_index2];
     int pref1 = preference[type1];
     int pref2 = preference[type2];
     for (int hwidx = 1; hwidx < nTh; ++hwidx) {
       if (addrP[hwidx].first.labels[top_index1] == id1 &&
           addrP[hwidx].first.labels[top_index2] != id2) {
         radix1 = false;
         break;
       }