st/omx/dec: set dst rect to match src size

st/omx/dec: set dst rect to match src size

When creating interlaced video buffer, hegith set to "template.height =
align(tmpl->height/ array_size, VL_MACROBLOCK_HEIGHT);", and we use
"template.height *= array_size;" for the buffer height, so it actually
aligned with 32. With progressive video buffer it still aligned with 16,
thus causing different height between interlaced buffer and progressive
buffer for 4K (height=2160), and 720p (height=720).

When transcode the video, this will cause the 16 lines corruption
at the bottom of the encode video.

Signed-off-by: Leo Liu <leo.liu@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>