[PATCH] mfplat/tests: Use correct interface macro.

[Marvin]

Hi,

While running your changed tests on Windows, I think I found new failures.
Being a bot and all I'm not very good at pattern recognition, so I might be
wrong, but could you please double-check?

Full results can be found at:
https://testbot.winehq.org/JobDetails.pl?Key=44057

Your paranoid android.


=== build (build log) ===

error: patch failed: dlls/mfplat/tests/mfplat.c:236
Task: Patch failed to apply

=== debian9 (build log) ===

error: patch failed: dlls/mfplat/tests/mfplat.c:236
Task: Patch failed to apply

=== debian9 (build log) ===

error: patch failed: dlls/mfplat/tests/mfplat.c:236
Task: Patch failed to apply