r600: Force NOPs when loading AR on R600 class hardware

r600: Force NOPs when loading AR on R600 class hardware

Loading indirectly from a register that was just written to
doesn't work on R600 class hardware, so add a NOP group with
the address register load being emitted in the t-slot. to make
sure that the register write was finished.

Fixes: 33765aa92aa5c150873fc210e9d6c1fe22cf8646
     r600/sfn: Enable NIR for pre RG hardware

Signed-off-by: Gert Wollny <gert.wollny@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/18130>