onnxInitGraph unconsistency between source files

[atupone]

onnxInitGraph is defined differently
between
foxi/onnxifi.h
and
foxi/onnxifi_wrapper.c

That does not allow building here

[cbartz]

Seems to have been introduced with #15 and #16, foxi/onnxifi_wrapper.c and foxi/onnxifi_dummy.c forgot to be updated.

The same goes for onnxWaitEventFor, the bug seems to have been introduced in #18, they forgot to update foxi/onnxifi_dummy.c.