[FasterTransformer] A simple bug in trt_model.h #498

Related to FasterTransformer/v2

Describe the bug
When I try to compile the FT V2, a bug was occur. Then I check it, I found there is a undefined variable called input_tensor, actually it should be from_tensor.

To Reproduce
cd V2;
mkdir build;
cmake .. -DBUILD_TRT=ON;
make

Expected behavior
A bug:
error: ‘input_tensor’ was not declared in this scope
assert(input_tensor);