i965: Stop XY clipping point and line primitives.

i965: Stop XY clipping point and line primitives.

Wide points and lines are not supposed to be clipped by the viewport.
Rather, they should be rendered, and any fragments outside of the
viewport should be discarded.

The traditional use case for this behavior is rendering moving wide
point particles.  When the center of the point approaches the viewport
edge, clipping would make it pop out of view early.

Fixes:
- dEQP-GLES2.functional.clipping.point.wide_point_clip
- dEQP-GLES3.functional.clipping.point.wide_point_clip
- dEQP-GLES3.functional.clipping.point.wide_point_clip_viewport_center
- dEQP-GLES3.functional.clipping.point.wide_point_clip_viewport_corner
- dEQP-GLES3.functional.clipping.line.wide_line_clip_viewport_center
- dEQP-GLES3.functional.clipping.line.wide_line_clip_viewport_corner

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=94453
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=94454
Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>