It is unsigned at least on arm, fixes the following warnings:
libavfilter/vf_signalstats.c:833:21: warning: taking the absolute value of unsigned type 'unsigned int' has no effect
            dify += abs(yuv - AV_RN16(prev->data[0] + pw + i * 2));

before this change, scale_vaapi hard coding the scaling mode, add a
new option "mode" to setting the scaling mode, it can be use to change
scaling algorithm for performance/quality trade off.

Note: VA_FILTER_SCALING_NL_ANAMORPHIC(nolinear ananorphic scaling
algorithm) doesn't support by i965/iHD driver now, add this just for
completeness.
Reviewed-by: Mark Thompson <sw@jkqxz.net>
Signed-off-by: Jun Zhao <mypopydev@gmail.com>

Fixes #6987.

abuffersink need to setting AV_OPT_FLAG_AUDIO_PARAM flag.
Reviewed-by: Nicolas George <george@nsup.org>
Signed-off-by: Jun Zhao <mypopydev@gmail.com>

Signed-off-by: Ruiling Song <ruiling.song@intel.com>
Signed-off-by: Mark Thompson <sw@jkqxz.net>

commit b0012de4 missed reindent.
Signed-off-by: Jun Zhao <mypopydev@gmail.com>

Reviewed-by: Paul B Mahol <onemda@gmail.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

Reviewed-by: Haihao Xiang <haihao.xiang@intel.com>
Signed-off-by: James Almer <jamrial@gmail.com>

Signed-off-by: Marton Balint <cus@passwd.hu>

Signed-off-by: Marton Balint <cus@passwd.hu>

After adding field type management to the common yadif logic, we can
remove the duplicate copy of that logic from bwdif.

The bwdif filter can use common yadif frame management if we track
when a field is the first or last field in a sequence. While this
information is not used by yadif, the added benefit of removing the
duplicated frame management logic makes it worth tracking this state
in the common code.

We have a pattern of wrapping CUDA calls to print errors and
normalise return values that is used in a couple of places. To
avoid duplication and increase consistency, let's put the wrapper
implementation in a shared place and use it everywhere.

Affects:

* avcodec/cuviddec
* avcodec/nvdec
* avcodec/nvenc
* avfilter/vf_scale_cuda
* avfilter/vf_scale_npp
* avfilter/vf_thumbnail_cuda
* avfilter/vf_transpose_npp
* avfilter/vf_yadif_cuda