Revert "r600/sfn: Make use of variable length DOT"

Revert "r600/sfn: Make use of variable length DOT"

This reverts commit fcafe1ffc85573b6a0df2d64a438f1bac2bae3a2.

Variable length DOT products are not supported for pre EG
cards, and the read port evaluation is not correctly
checked, so that scheduling might fail. Revert for now to
fix the issues below and get gack with a better implementation
later.

Closes: https://gitlab.freedesktop.org/mesa/mesa/-/issues/7876
Related: https://gitlab.freedesktop.org/mesa/mesa/-/issues/7878

Signed-off-by: Gert Wollny <gert.wollny@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/20268>