logd: 64-bit compile issue

- ULONG_MAX is used against an uint32
- Add tv_sec_max and tv_nsec_max constants to log_time

Change-Id: Ic86cd7b0680868ad0536198b71a34cb19134fc22
diff --git a/logd/LogStatistics.cpp b/logd/LogStatistics.cpp
index f2b9a26..81c9bab 100644
--- a/logd/LogStatistics.cpp
+++ b/logd/LogStatistics.cpp
@@ -392,8 +392,8 @@
 
     dgram_qlen_statistics = false;
     for(unsigned short bucket = 0; dgram_qlen(bucket); ++bucket) {
-        mMinimum[bucket].tv_sec = (uint32_t)-1;
-        mMinimum[bucket].tv_nsec = 999999999UL;
+        mMinimum[bucket].tv_sec = mMinimum[bucket].tv_sec_max;
+        mMinimum[bucket].tv_nsec = mMinimum[bucket].tv_nsec_max;
     }
 }
 
@@ -439,7 +439,7 @@
 }
 
 unsigned long long LogStatistics::minimum(unsigned short bucket) {
-    if (mMinimum[bucket].tv_sec == LONG_MAX) {
+    if (mMinimum[bucket].tv_sec == mMinimum[bucket].tv_sec_max) {
         return 0;
     }
     return mMinimum[bucket].nsec();