uapi: amend interlace buffer size calculation condition

Interlace video playback is failed for resolutions like 1600x1200
due to insufficient buffer size. Avoid the issue by correcting
interlace video buffer size calculation condition.

Change-Id: Ieaf9b62c75c0766f268eb1178be83bf17f0de7d5
Signed-off-by: Govindaraj Rajagopal <grajagop@codeaurora.org>