drm/amdgpu/gfx9: manually control gfxoff for CS on RV

drm/amdgpu/gfx9: manually control gfxoff for CS on RV

When mesa started using compute queues more often
we started seeing additional hangs with compute queues.
Disabling gfxoff seems to mitigate that.  Manually
control gfxoff and gfx pg with command submissions to avoid
any issues related to gfxoff.  KFD already does the same
thing for these chips.

v2: limit to compute
v3: limit to APUs
v4: limit to Raven/PCO
v5: only update the compute ring_funcs
v6: Disable GFX PG
v7: adjust order

Reviewed-by: Lijo Lazar <lijo.lazar@amd.com>
Suggested-by: Błażej Szczygieł <mumei6102@gmail.com>
Suggested-by: Sergey Kovalenko <seryoga.engineering@gmail.com>
Link: https://gitlab.freedesktop.org/drm/amd/-/issues/3861
Link: https://lists.freedesktop.org/archives/amd-gfx/2025-January/119116.html
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org # 6.12.x