Use __arm__ instead of ARCH_ARM.

Change-Id: I777da5757f01d8328d5475e654d56d81dc802655
diff --git a/libutils/SystemClock.cpp b/libutils/SystemClock.cpp
index dbad581..ac3dd98 100644
--- a/libutils/SystemClock.cpp
+++ b/libutils/SystemClock.cpp
@@ -68,7 +68,7 @@
  */
 #define DEBUG_TIMESTAMP         0
 
-#if DEBUG_TIMESTAMP && defined(ARCH_ARM)
+#if DEBUG_TIMESTAMP && defined(__arm__)
 static inline void checkTimeStamps(int64_t timestamp,
                                    int64_t volatile *prevTimestampPtr,
                                    int volatile *prevMethodPtr,