encoder: h264: fix C90 mixed declarations and code
encoder: h264: fix C90 mixed declarations and code

Commit 4259d1a introduced this compilation error. This patch fixes it.

01org/iotg-lin-gfx-gstreamer-vaapi,01org/iotg-lin-gfx-gstreamer-vaapi,01org/iotg-lin-gfx-gstreamer-vaapi