frameworks/rs: fix typos and clang-tidy warnings

This change fixes a few typos and clang tidy warnings related to the
"llvm-namespace-comment" checks.

Bug: 26936282
Test: WITH_TIDY=1 WITH_TIDY_CHECKS="llvm-namespace-comment" mm
Change-Id: Ic65182e5b4999fbd48d6a8ad7172e4bfeeb541f4
diff --git a/cpu_ref/rsd_cpu.h b/cpu_ref/rsd_cpu.h
index 46c1743..130e6ac 100644
--- a/cpu_ref/rsd_cpu.h
+++ b/cpu_ref/rsd_cpu.h
@@ -148,7 +148,7 @@
 };
 
 
-}
-}
+} // namespace renderscript
+} // namespace android
 
 #endif