freedreno/a6xx: smaller hammer for fb barrier

We just need to do a sequence of commands to flush the cache.

Signed-off-by: Rob Clark <robdclark@chromium.org>
14 jobs for !766 with wip/blend-equation-advanced in 8 minutes and 7 seconds (queued for 5 seconds)
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Status Job ID Name Coverage
  Containers Build
passed #271171
debian

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  Build+Test
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meson-clang

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meson-gallium-clover-llvm

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meson-gallium-clover-llvm39

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meson-gallium-drivers-other

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meson-gallium-radeonsi

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meson-gallium-st-other

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meson-gallium-swr

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meson-glvnd

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meson-loader-classic-dri

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meson-vulkan

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scons-llvm

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scons-nollvm

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scons-swr

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