media: verisilicon: Fix IMX8 native pixel-format step values

The Hantro decoder non post-processed pixel-format steps are different
from the post-processed ones. Fix the steps according to the hardware
limitations. Since reference frame pixel-format issues have been fixed,
it is possible to use V4L2_PIX_FMT_NV15_4L4 rather V4L2_PIX_FMT_P010_4L4
for 10bit streams.

Fluster VP9 score goes up to 207/305.
HEVC score is still 141/147.

Signed-off-by: Benjamin Gaignard <benjamin.gaignard@collabora.com>
Reviewed-by: Nicolas Dufresne <nicolas.dufresne@collabora.com>
Signed-off-by: Sebastian Fricke <sebastian.fricke@collabora.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>