Remove functionality unsupported by the JIT from multi_head_attention_forward. (#20653)
Summary:
Remove the internal functions in multi_head_attention_forward. Those internal functions cause 10-15% performance regression and there is possibly a JIT issue.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/20653
Differential Revision: D15398888
Pulled By: cpuhrsch
fbshipit-source-id: 0a3f053a4ade5009e73d3974fa6733c2bff9d929
