Set _updateFreeMemoryMinPeriod option to 300 ms on Power

The current default value for this option (50 ms) has been shown
to cause a small footprint regression on Power. This commit changes
the default value of `_updateFreeMemoryMinPeriod` to 300 ms on Power
to eliminate the regression.

Signed-off-by: Marius Pirvu <mpirvu@ca.ibm.com>

runtime/compiler/control/J9Options.cpp

@@ -266,8 +266,11 @@ int32_t J9::Options::_numCodeCachesToCreateAtStartup = 0; // 0 means no change f
 int32_t J9::Options::_dataCacheQuantumSize = 64;
 int32_t J9::Options::_dataCacheMinQuanta = 2;
 
+#if defined(TR_TARGET_POWER)
+int32_t J9::Options::_updateFreeMemoryMinPeriod = 300;  // 300 ms
+#else
 int32_t J9::Options::_updateFreeMemoryMinPeriod = 50;  // 50 ms
-
+#endif /* defined(TR_TARGET_POWER) */
 size_t J9::Options::_scratchSpaceLimitKBWhenLowVirtualMemory = 64*1024; // 64MB; currently, only used on 32 bit Windows
 
 int32_t J9::Options::_scratchSpaceFactorWhenJSR292Workload = JSR292_SCRATCH_SPACE_FACTOR;