st/nine: Fix computation of const_used_size
st/nine: Fix computation of const_used_size

Was sometimes too large for PS.

Reviewed-by: Axel Davy <2b6ef604b998fb81662f85c329e4fc020eae8e5d@ens.fr>
Signed-off-by: Xavier Bouchoux <e9cfce4fcf378facd135f8db23dca45dea57fb90@gmail.com>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler