r300g: only set clip_halfz for chips with HW TCL
r300g: only set clip_halfz for chips with HW TCL

I forgot that we cannot emit vertex shader state on a chip without VS.
In such a case, clip_halfz is handled by the Draw module.

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler