drm/i915: Disable RPG during live selftest

drm/i915: Disable RPG during live selftest

The Forcewake timeout issue has been observed on Gen 12.0 and above.
To address this, disable Render Power-Gating (RPG) during live self-tests
for these generations. The temporary workaround 'drm/i915/mtl: do not
enable render power-gating on MTL' disables RPG globally, which is
unnecessary since the issues were only seen during self-tests.

v2: take runtime pm wakeref

Closes: https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/9413
Fixes: 25e7976db86b ("drm/i915/mtl: do not enable render power-gating on MTL")
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Andi Shyti <andi.shyti@intel.com>
Cc: Andrzej Hajda <andrzej.hajda@intel.com>
Signed-off-by: Badal Nilawar <badal.nilawar@intel.com>
Signed-off-by: Sk Anirban <sk.anirban@intel.com>
Reviewed-by: Karthik Poosa <karthik.poosa@intel.com>
Signed-off-by: Anshuman Gupta <anshuman.gupta@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20250310152821.2931678-1-sk.anirban@intel.com
(cherry picked from commit 0a4ae87706c6d15d14648e428c3a76351f823e48)
Signed-off-by: Jani Nikula <jani.nikula@intel.com>