Power: disable a bunch of things

BROKE intel arc A380 completely because it was forced into L1.1/L1.2
pcie substates. Forcewaking the device would fail and it would never come up.

So I will be more conservative on power saving tuning.

configuration.nix

@@ -120,7 +120,12 @@
     };
   };
 
-  hardware.intelgpu.driver = "xe";
+  # Intel Arc A380 (DG2, 56a5) uses the i915 driver on kernel 6.12.
+  # The xe driver's iHD media driver integration has buffer mapping
+  # failures on this GPU/kernel combination. i915 works correctly for
+  # VAAPI transcode as long as ASPM deep states are disabled for the
+  # GPU (see modules/power.nix).
+  hardware.intelgpu.driver = "i915";
 
   # Per-service 2MB hugepage budget calculated in service-configs.nix.
   boot.kernel.sysctl."vm.nr_hugepages" = service_configs.hugepages_2m.total_pages;