Fixed configuration file for alexnet2

llvm/test/VISC/DNN_Benchmarks/benchmarks/alexnet2/data/tuner_confs.txt

 +++++
 conf1 3.86 82.91
 1 gpu conv perf 1 add fp32 1 tanh fp32 1 
-2 gpu conv perf 2 add fp32 1 tanh fp32 1 pool fp32 1
+2 gpu conv perf 2 add fp32 1 tanh fp32 1 pool_max fp32 1
 3 promise swing_level 4
 4 promise swing_level 4
 5 promise swing_level 4