iris: Handle vertex shader with window space position
Iris advertises support for PIPE_CAP_TGSI_VS_WINDOW_SPACE_POSITION so let's actually implement it. Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=110657 Signed-off-by: Danylo Piliaiev <danylo.piliaiev@globallogic.com> Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>