drm/i915: Free the returned object of acpi_evaluate_dsm()

As per the comment on top of acpi_evaluate_dsm():

| * Evaluate device's _DSM method with specified GUID, revision id and
| * function number. Caller needs to free the returned object.

We should free the returned object of acpi_evaluate_dsm() to avoid memory
leakage. Otherwise the kmemleak splat will be triggered at boot time (if we
compile kernel with CONFIG_DEBUG_TEST_DRIVER_REMOVE=y).

Fixes: 8e55f99c ("drm/i915: Invoke another _DSM to enable MUX on HP Workstation laptops")
Cc: Kai-Heng Feng <kai.heng.feng@canonical.com>
Signed-off-by: Zenghui Yu <yuzenghui@huawei.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210906033541.862-1-yuzenghui@huawei.com
(cherry picked from commit 149ac2e7)
Signed-off-by: Jani Nikula <jani.nikula@intel.com>

drivers/gpu/drm/i915/display/intel_acpi.c

@@ -186,13 +186,16 @@ void intel_dsm_get_bios_data_funcs_supported(struct drm_i915_private *i915)
 {
 	struct pci_dev *pdev = to_pci_dev(i915->drm.dev);
 	acpi_handle dhandle;
+	union acpi_object *obj;
 
 	dhandle = ACPI_HANDLE(&pdev->dev);
 	if (!dhandle)
 		return;
 
-	acpi_evaluate_dsm(dhandle, &intel_dsm_guid2, INTEL_DSM_REVISION_ID,
-			  INTEL_DSM_FN_GET_BIOS_DATA_FUNCS_SUPPORTED, NULL);
+	obj = acpi_evaluate_dsm(dhandle, &intel_dsm_guid2, INTEL_DSM_REVISION_ID,
+				INTEL_DSM_FN_GET_BIOS_DATA_FUNCS_SUPPORTED, NULL);
+	if (obj)
+		ACPI_FREE(obj);
 }
 
 /*