drm/amdgpu/acpi: make ATPX/ATCS structures global (v2)

They are global ACPI methods, so maybe the structures
global in the driver. This simplified a number of things
in the handling of these methods.

v2: reset the handle if verify interface fails (Lijo)
v3: fix compilation when ACPI is not defined.

Reviewed-by: Lijo Lazar <lijo.lazar@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
index 0e39c1b..e538324 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -3415,7 +3415,7 @@ static void amdgpu_dm_update_backlight_caps(struct amdgpu_display_manager *dm)
 	if (dm->backlight_caps.caps_valid)
 		return;
 
-	amdgpu_acpi_get_backlight_caps(dm->adev, &caps);
+	amdgpu_acpi_get_backlight_caps(&caps);
 	if (caps.caps_valid) {
 		dm->backlight_caps.caps_valid = true;
 		if (caps.aux_support)