5045 use atomic_{inc,dec}_* instead of atomic_add_*

@@ -315,11 +315,11 @@
     uint_t nhashwon;
     uint_t nnotfound;
 } memseg_stats;
 
 #define MEMSEG_STAT_INCR(v) \
-        atomic_add_32(&memseg_stats.v, 1)
+        atomic_inc_32(&memseg_stats.v)
 #else
 #define MEMSEG_STAT_INCR(x)
 #endif
 
 struct memseg *memsegs;         /* list of memory segments */