Enable benchmark after trim, when requested.

The framework can request that a benchmark be run after an fstrim,
but it was disabled due to a kernel bug on certain devices.  That bug
has long been fixed, so it should be safe to enable this again.

Bug: 23942769
Change-Id: Ibe967a75856d0cbad45e2f8f3120f1970caf36d0

TrimTask.cpp

@@ -37,7 +37,7 @@
 /* From a would-be kernel header */
 #define FIDTRIM         _IOWR('f', 128, struct fstrim_range)    /* Deep discard trim */
 
-#define BENCHMARK_ENABLED 0
+#define BENCHMARK_ENABLED 1
 
 using android::base::StringPrintf;