entity_name: cleanup headers
entity_name: cleanup headers

Drop unused headers, add missing explicit header.

Change-Id: I35d94ba205cef677e59620c24e27ec0bffba7743
Signed-off-by: Patrick Venture <36c53fa43f47f3fd67cb2fc38031827244d18a1f@google.com>

openbmc/google-ipmi-sys