anv: Optimize blend state

If color attachment format does not have alpha but one of the blend
factors is DST_ALPHA or ONE_MINUS_DST_ALPHA/SRC_ALPHA_SATURATE, we can
replace it with ONE or ZERO respectively.

Signed-off-by: Sagar Ghuge <sagar.ghuge@intel.com>
25 jobs for !88 with blend_state in 55 minutes and 13 seconds (queued for 57 minutes and 1 second)
latest detached
Status Job ID Name Coverage
  Containers Build
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containers:ubuntu

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  Build+Test
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build:make-gallium-drivers-other

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build:make-gallium-drivers-radeonsi

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build:make-gallium-drivers-swr

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build:make-gallium-st-clover-llvm-39

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build:make-gallium-st-clover-llvm-4

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build:make-gallium-st-clover-llvm-5

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build:make-gallium-st-clover-llvm-6

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build:make-gallium-st-clover-llvm-7

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build:make-gallium-st-other

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build:make-loader-classic-dri

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build:make-vulkan

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build:meson-gallium-clover-llvm5

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build:meson-gallium-clover-llvm6

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build:meson-gallium-clover-llvm7

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build:meson-gallium-drivers-other

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build:meson-gallium-radeonsi

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build:meson-gallium-st-other

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build:meson-gallium-swr

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build:meson-glvnd

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build:meson-loader-classic-dri

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build:meson-vulkan

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build:scons-llvm

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build:scons-nollvm

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build:scons-swr

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