Add MPT-7B-instruct HuggingFace Model (#1773)
Summary:
PR to add https://huggingface.co/mosaicml/mpt-7b-instruct in torchbenchmark.
Running mpt-7b-instruct requires ```trust_remote_code``` to be passed
Pull Request resolved: https://github.com/pytorch/benchmark/pull/1773
Reviewed By: msaroufim
Differential Revision: D48031826
Pulled By: xuzhao9
fbshipit-source-id: d3cada22894544a88409ef11ccd4b0b101507a2a
