add OP:NonZero to op_list.md
| 37 | Ceil | 38 | Concat | 39 | Flatten | 40 | ConvTranspose |
| 41 | MatMul | 42 | Sum | 43 | Transpose | 44 | BatchNormalization |
| 45 | Squeeze | 46 | Equal | 47 | Identity | 48 | GlobalAveragePool |
-| 49 | MaxPool | 50 | Conv | 51 | Gemm |
+| 49 | MaxPool | 50 | Conv | 51 | Gemm | 52 | NonZero |
