util: Change os_same_file_description return type from bool to int

This allows communicating that it wasn't possible to determine whether
the two file descriptors reference the same file description. When
that's the case, log a warning in the amdgpu winsys.

In turn, remove the corresponding debugging output from the fallback
os_same_file_description implementation. It depends on the caller if
false negatives are problematic or not.

Reviewed-by: Eric Engestrom <eric@engestrom.ch>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Tested-by: Marge Bot <!3879>
Part-of: <!3879>
(cherry picked from commit f5a89589)
38 jobs for staging/20.0 in 24 minutes and 43 seconds (queued for 3 seconds)
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aarch64
arm_build

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arm_test

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x86_build

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x86_build_old

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x86_test-gl

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  Build
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aarch64
meson-arm64

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aarch64
meson-arm64-build-test

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aarch64
meson-armhf

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meson-clang

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meson-clover

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meson-clover-old-llvm

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meson-i386

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meson-main

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meson-mingw32-x86_64

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meson-testing

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meson-vulkan

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scons

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scons-swr

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  Test
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db410c
arm64_a306_gles2

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mesa-cheza
arm64_a630_gles2

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mesa-cheza
arm64_a630_gles31

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mesa-ci-aarch64-lava-collabora
panfrost-t720-test:arm64

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mesa-ci-aarch64-lava-collabora
panfrost-t760-test:armhf

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mesa-ci-aarch64-lava-collabora
panfrost-t860-test:arm64

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piglit-glslparser

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piglit-quick_gl

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piglit-quick_shader

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test-llvmpipe-gles2

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