nir/lower_point_size: assume scalar PSIZ

Reviewed-by: Erik Faye-Lund <erik.faye-lund@collabora.com>
Reviewed-by: Eric Anholt <eric@anholt.net>
22 jobs for !1868 with nir_psiz_scalar in 14 minutes and 56 seconds (queued for 6 seconds)
merge request