drm_hwcomposer: Fix header compilation for C

Change-Id: I07ff3f16f3542071b42cfaa6b294017e54a84c4a
Reviewed-on: https://chrome-internal-review.googlesource.com/203636
Reviewed-by: Stéphane Marchesin <marcheu@google.com>
Commit-Queue: Stéphane Marchesin <marcheu@google.com>
Tested-by: Stéphane Marchesin <marcheu@google.com>
1 file changed