i965: Fix point size with tessellation/geometry shaders in GLES.

i965: Fix point size with tessellation/geometry shaders in GLES.

Our previous code worked for desktop GL, and ES without geometry or
tessellation shaders.  But those features require fancier point size
handling.  Fortunately, we can use one rule for all APIs.

Fixes a number of dEQP tests with EXT_tessellation_shader enabled:
dEQP-GLES31.functional.tessellation_geometry_interaction.point_size.*

Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Acked-by: Ilia Mirkin <imirkin@alum.mit.edu>
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>