CHROMIUM: s5p-mfc: Don't change the image size to smaller than the request.

Use the requested size as the minimum bound, unless it's less than the
required hardware minimum. The bound align function will align to the
closest value but we do not want to adjust below the requested size.

Signed-off-by: Wu-Cheng Li <wuchengli@chromium.org>

BUG=chromium:381444
TEST=webrtc call and VEA unittest.

Change-Id: I1c70447b9be4e09095862fb828903c32fd594269
Reviewed-on: https://chromium-review.googlesource.com/203388
Reviewed-by: Pawel Osciak <posciak@chromium.org>
Tested-by: Wu-Cheng Li <wuchengli@chromium.org>
Commit-Queue: Haixia Shi <hshi@chromium.org>
(cherry picked from commit cbdb1f9c90c94979350fa72f08ea7cb5f9e81f7b)
Reviewed-on: https://chromium-review.googlesource.com/204250
Commit-Queue: Pawel Osciak <posciak@chromium.org>
Tested-by: Pawel Osciak <posciak@chromium.org>