Follow up of "div/rem on x86 and x86_64", to tidy up the code a little.

Change-Id: Ibf39cbc8ac1d773599d70be2cb1e941674b60f1d
diff --git a/compiler/optimizing/code_generator_utils.h b/compiler/optimizing/code_generator_utils.h
index 742d675..59b495c 100644
--- a/compiler/optimizing/code_generator_utils.h
+++ b/compiler/optimizing/code_generator_utils.h
@@ -19,7 +19,12 @@
 
 #include <cstdint>
 
-// Computes the magic number and the shift needed in the div/rem by constant algorithm
+namespace art {
+
+// Computes the magic number and the shift needed in the div/rem by constant algorithm, as out
+// arguments `magic` and `shift`
 void CalculateMagicAndShiftForDivRem(int64_t divisor, bool is_long, int64_t* magic, int* shift);
 
+}  // namespace art
+
 #endif  // ART_COMPILER_OPTIMIZING_CODE_GENERATOR_UTILS_H_