[OpenMP] Add missing parenthesis which triggers a compile error

[grokos]

Summary

Compiling with -Werror triggers an error due to a missing pair of parentheses:

error: using the result of an assignment as a condition without parentheses [-Werror,-Wparentheses]

[AndreyChurbanov]

LGTM

openmp/trunk/runtime/src/kmp_settings.cpp

__kmp_stg_parse_hw_subset( char const * name, char const * value, void * data ) {
   }
   if (len == 0 || mlen == 0)
     goto err; // contents is either empty or too long
   input[len] = '\0';
   __kmp_hws_requested = 1; // mark that subset requested
   // Split by delimiter
   pos = input;
   components[level++] = pos;
-  while (pos = strchr(pos, ',')) {
+  while ((pos = strchr(pos, ','))) {
     *pos = '\0'; // modify input and avoid more copying
     components[level++] = ++pos; // expect something after ","
     if (level > MAX_T_LEVEL)
       goto err; // too many components provided
   }
   // Check each component
   for (int i = 0; i < level; ++i) {
     int offset = 0;