st/glsl_to_tgsi: fix a corner case of std140 layout in uniform buffers
st/glsl_to_tgsi: fix a corner case of std140 layout in uniform buffers

See the comment in the code for an explanation. This fixes
GL45-CTS.buffer_storage.map_persistent_draw.

Reviewed-by: Marek Olšák <8c7344a1abdb103e79ecfd488098373070c3c70e@amd.com>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler