drm/amd: Disallow s0ix without BIOS support again

commit cf488dcd0a ("drm/amd: Allow s0ix without BIOS support") showed
improvements to power consumption over suspend when s0ix wasn't enabled in
BIOS and the system didn't support S3.

This patch however was misguided because the reason the system didn't
support S3 was because SMT was disabled in OEM BIOS setup.
This prevented the BIOS from allowing S3.

Also allowing GPUs to use the s2idle path actually causes problems if
they're invoked on systems that may not support s2idle in the platform
firmware. `systemd` has a tendency to try to use `s2idle` if `deep` fails
for any reason, which could lead to unexpected flows.

The original commit also fixed a problem during resume from suspend to idle
without hardware support, but this is no longer necessary with commit
ca47518663 ("drm/amd: Don't allow s0ix on APUs older than Raven")

Revert commit cf488dcd0a ("drm/amd: Allow s0ix without BIOS support")
to make it match the expected behavior again.

Cc: Rafael Ávila de Espíndola <rafael@espindo.la>
Link: https://github.com/torvalds/linux/blob/v6.1/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c#L1060
Closes: https://gitlab.freedesktop.org/drm/amd/-/issues/2599
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c

@@ -1499,16 +1499,20 @@ bool amdgpu_acpi_is_s0ix_active(struct amdgpu_device *adev)
 	 * S0ix even though the system is suspending to idle, so return false
 	 * in that case.
 	 */
-	if (!(acpi_gbl_FADT.flags & ACPI_FADT_LOW_POWER_S0))
+	if (!(acpi_gbl_FADT.flags & ACPI_FADT_LOW_POWER_S0)) {
 		dev_warn_once(adev->dev,
 			      "Power consumption will be higher as BIOS has not been configured for suspend-to-idle.\n"
 			      "To use suspend-to-idle change the sleep mode in BIOS setup.\n");
+		return false;
+	}
 
 #if !IS_ENABLED(CONFIG_AMD_PMC)
 	dev_warn_once(adev->dev,
 		      "Power consumption will be higher as the kernel has not been compiled with CONFIG_AMD_PMC.\n");
-#endif /* CONFIG_AMD_PMC */
+	return false;
+#else
 	return true;
+#endif /* CONFIG_AMD_PMC */
 }
 
 #endif /* CONFIG_SUSPEND */