media: hantro: sunxi: Fix VP9 steps

It turns out that postproc on Allwinner H6 needs width and height to be
multiple of 32.

Fixes: 86790a4f ("media: hantro: Add support for Allwinner H6")
Signed-off-by: Jernej Skrabec <jernej.skrabec@gmail.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>