zink: move viewport count to zink_gfx_pipeline_state

this is part of the pipeline state (there's an extension for setting it
dynamically but we don't supprot that atm

Reviewed-by: Erik Faye-Lund <erik.faye-lund@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6349>
4 files changed