[libc] [gpu] Change Time To Be Per Iteration (llvm#101919)

Previously, the time field was the total time take to run all iterations
of the benchmark. This PR changes the value displayed to be the average
time take by each iteration.

Author: jameshu15869

libc/benchmarks/gpu/LibcGpuBenchmark.cpp

@@ -115,7 +115,7 @@ void print_results(Benchmark *b) {
   cpp::atomic_thread_fence(cpp::MemoryOrder::RELEASE);
 
   LIBC_NAMESPACE::printf(
-      "%-20s |%8ld |%8ld |%8ld |%11d |%9ld %2s |%9ld |%9d |\n",
+      "%-20s |%8ld |%8ld |%8ld |%11d |%14ld %2s |%9ld |%9d |\n",
       b->get_test_name().data(), result.cycles, result.min, result.max,
       result.total_iterations, result.total_time, time_unit,
       static_cast<uint64_t>(result.standard_deviation), num_threads);
@@ -126,9 +126,9 @@ void print_header() {
   LIBC_NAMESPACE::printf("Running Suite: %-10s\n",
                          benchmarks[0]->get_suite_name().data());
   LIBC_NAMESPACE::printf("%s", RESET);
-  LIBC_NAMESPACE::printf("Benchmark            |  Cycles |     Min |     Max | "
-                         "Iterations |        "
-                         "Time |   Stddev |  Threads |\n");
+  LIBC_NAMESPACE::printf(
+      "Benchmark            |  Cycles |     Min |     Max | "
+      "Iterations | Time / Iteration |   Stddev |  Threads |\n");
   LIBC_NAMESPACE::printf(
       "---------------------------------------------------------------------"
       "--------------------------------\n");
@@ -222,7 +222,7 @@ BenchmarkResult benchmark(const BenchmarkOptions &options,
   result.max = max;
   result.samples = samples;
   result.total_iterations = total_iterations;
-  result.total_time = total_time;
+  result.total_time = total_time / total_iterations;
   return result;
 };