AArch64: Add USMMLA impl. for SBD 6-tap H/HV filters

Add 6-tap variant of standard bit-depth horizontal subpel filters using the Armv8.6 I8MM USMMLA matrix multiply instruction. This patch also extends the HV filter with 6-tap horizontal pass using USMMLA.

This MR also contains a typo fix in the SBD 6-tap 2D/HV subpel filter.

Benchmarks show up-to 6-7% FPS increase depending on the input video and the CPU used.

This patch will increase the .text by around 1.2 KiB.

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Relative runtime of micro benchmarks after this patch on Neoverse and Cortex CPU cores:

regular      V2      V1      X3    A720    A715    A520    A510
  w8 hv:  0.860x  0.895x  0.870x  0.896x  0.896x  0.938x  0.936x
 w16 hv:  0.829x  0.886x  0.865x  0.908x  0.906x  0.946x  0.944x
 w32 hv:  0.837x  0.883x  0.862x  0.914x  0.915x  0.953x  0.949x
 w64 hv:  0.840x  0.883x  0.862x  0.914x  0.914x  0.955x  0.952x

  w8 h:   0.746x  0.754x  0.747x  0.723x  0.724x  0.874x  0.866x
 w16 h:   0.749x  0.764x  0.745x  0.731x  0.731x  0.858x  0.852x
 w32 h:   0.739x  0.754x  0.738x  0.729x  0.729x  0.839x  0.837x
 w64 h:   0.736x  0.749x  0.733x  0.725x  0.726x  0.847x  0.836x

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Some benchmark results for USMMLA version against using USDOT:

Models 1080p:

AWS Graviton 3:  193.69 fps  ->  200.04 fps ( +3.28% )
AWS Graviton 4:  246.09 fps  ->  255.00 fps ( +3.62% )

Balloons 1080p:

AWS Graviton 3:  176.33 fps  ->  180.61 fps ( +2.43% )

AWS Graviton 4:  225.18 fps  ->  231.24 fps ( +2.69% )

Mountain Bike 1080p:

AWS Graviton 3:  144.80 fps  ->  147.89 fps ( +2.13% )
AWS Graviton 4:  183.44 fps  ->  187.38 fps ( +2.15% )

Nature 1080p:

AWS Graviton 3:  140.22 fps  ->  142.42 fps ( +1.57% )
AWS Graviton 4:  178.17 fps  ->  181.14 fps ( +1.67% )

Vision Pro 1080p:

AWS Graviton 3:  200.66 fps  ->  205.25 fps ( +2.29% )
AWS Graviton 4:  260.92 fps  ->  266.68 fps ( +2.21% )

Bosphorus:

AWS Graviton 3 - 720p:   540.45 fps  ->  580.43 fps ( +7.40% )
AWS Graviton 4 - 720p:   680.19 fps  ->  724.72 fps ( +6.55% )

AWS Graviton 3 - 1080p:  242.12 fps  ->  256.48 fps ( +5.93% )
AWS Graviton 4 - 1080p:  305.77 fps  ->  326.12 fps ( +6.66% )

AWS Graviton 3 - 2160p:   60.60 fps  ->   63.37 fps ( +4.57% )
AWS Graviton 4 - 2160p:   76.71 fps  ->   80.69 fps ( +5.19% )

Bosphorus videos were encoded by aomenc (3.7.1+):

aomenc --good --cpu-used=5 -w 1280 -h  720 --bit-depth=8 --ivf -o Bosphorus_720p_8bit.ivf  Bosphorus_1920x1080_120fps_420_8bit_YUV.y4m
aomenc --good --cpu-used=5 -w 1920 -h 1080 --bit-depth=8 --ivf -o Bosphorus_1080p_8bit.ivf Bosphorus_1920x1080_120fps_420_8bit_YUV.y4m
aomenc --good --cpu-used=5 -w 3840 -h 2160 --bit-depth=8 --ivf -o Bosphorus_2160p_8bit.ivf Bosphorus_3840x2160_120fps_420_8bit_YUV.y4m