[rtl/entropy_src] Add entropy_src to MakeFile
[rtl/entropy_src] Add entropy_src to MakeFile

This PR adds entropy_src to MakeFile so the auto-generated updates will
be applied to it

Signed-off-by: Cindy Chen <399ad771a111eac8923348b1e2af093034e5d4f1@google.com>

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