NetFn: Use api.hpp instead of api.h

Since NetFn declared in api.h has been gradually deprecated, this
submission is to use api.hpp instead of api.h.

https://gerrit.openbmc.org/c/openbmc/phosphor-host-ipmid/+/79391

Change-Id: I6f15b2de43d976bf626e494ca70bad9d8cdd55fc
Signed-off-by: George Liu <liuxiwei@ieisystem.com>
4 files changed