i965: Move legacy clip plane handling to vec4_vs_visitor.

i965: Move legacy clip plane handling to vec4_vs_visitor.

This is now only used for the vertex shader, so it makes sense to get it
out of any paths run by the geometry shader.

Instead of passing the gl_clip_plane array into the run() method (which
is shared among all subclasses), we add it as a vec4_vs_visitor
constructor parameter.  This eliminates the bogus NULL parameter in the
GS case.

Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Chris Forbes <chrisf@ijw.co.nz>