zink: fix pointcoord y inversion

zink: fix pointcoord y inversion

Point sprite coordinates in general need to be inverted,
not just the texcoords converted to point sprite.

Move point coord y inversion out to its own pass.
Fixes GTF-GL46.gtf21.GL2FixedTests.point_sprites.point_sprites
with FBO dEQP surface.

cc: mesa-stable

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/21050>