gallium/cso: only enable compute shaders when TGSI is supported
gallium/cso: only enable compute shaders when TGSI is supported

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=94186
Signed-off-by: Samuel Pitoiset <506e97eed81d9e59d22f4c73fb51123bb62b4a30@gmail.com>
Reviewed-by: Marek Olšák <8c7344a1abdb103e79ecfd488098373070c3c70e@amd.com>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler