r600/sfn; go back to not lowering uniforms to UBOs

r600/sfn; go back to not lowering uniforms to UBOs

Lowering uniforms to UBOs results in an aditional iadd for the
UBO buffer id evaluation, and for indirect buffers access that
results in an unnecessary op that can be avoided by not lowering
uniforms. There is some code duplication when reading the uniforms
but it saves a whole instruction group per indirect cont buffer
access.

This reverts commit 98eb00face93b9af5aac19008ecff5a2bf376745 with
some additional fixes.

Signed-off-by: Gert Wollny <gert.wollny@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6879>