main: unreference ATIFragmentShader program before creating new one

Old program was overwritten without release of memory.

Signed-off-by: Yevhenii Kolesnikov <yevhenii.kolesnikov@globallogic.com>
Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
13 jobs for !1460 with fix/memleak_atifragmentshader in 9 minutes and 11 seconds (queued for 25 seconds)
latest detached
Status Job ID Name Coverage
  Containers Build
passed #449764
debian

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  Build+Test
passed #449773
meson-arm64

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passed #449772
meson-armhf

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passed #449766
meson-clang

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passed #449770
meson-clover

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passed #449774
meson-i386

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passed #449769
meson-main

00:05:37

passed #449765
meson-swr-glvnd

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passed #449771
meson-vulkan

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passed #449776
scons-llvm

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passed #449775
scons-nollvm

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passed #449767
scons-swr

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passed #449768
scons-win64

00:07:47