[TOPI] Support LRN Operator

[renjiangyong]

when I running the vgg model on nnvm, I got an error "Operator: LRN is not supported in nnvm", maybe the LRN is not implement, Did we have a plan to support LRN layer in nnvm, pls tell me the schedule when have a plan. thank you very much!

jiangyong

[kevinthesun]

VGG pretrained model in gluon can be directly imported into nnvm and run. Have you tried that?

[tqchen]

LRN itself can be supported by composing the current reduction and broadcast based operators, contribution is more than welcomed

[PariksheetPinjari909]

LRN support is added #1000