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
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