radeonsi: gate PIPE_CAP_SHADER_BUFFER_OFFSET_ALIGNMENT by LLVM version
radeonsi: gate PIPE_CAP_SHADER_BUFFER_OFFSET_ALIGNMENT by LLVM version

Otherwise we incorrectly claim ARB_ssbo support even with older LLVM versions.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=94917
Reviewed-by: Michel Dänzer <242b79f0804cf52679d58f27ed754158c1323c75@amd.com>
Reviewed-by: Bas Nieuwenhuizen <1d31d94f30d40df7951505d1034e1e923d02ec49@basnieuwenhuizen.nl>
Reviewed-by: Marek Olšák <8c7344a1abdb103e79ecfd488098373070c3c70e@amd.com>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler