drm/amdgpu: Fix potential double free and null pointer dereference

In amdgpu_get_xgmi_hive(), we should not call kfree() after
kobject_put() as the PUT will call kfree().

In amdgpu_device_ip_init(), we need to check the returned *hive*
which can be NULL before we dereference it.

Signed-off-by: Liang He <[e-mail]>
Reviewed-by: Luben Tuikov <[e-mail]>
Signed-off-by: Alex Deucher <[e-mail]>

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

···
 			if (!amdgpu_sriov_vf(adev)) {
 				struct amdgpu_hive_info *hive = amdgpu_get_xgmi_hive(adev);
 
+				if (WARN_ON(!hive)) {
+					r = -ENOENT;
+					goto init_failed;
+				}
+
 				if (!hive->reset_domain ||
 				    !amdgpu_reset_get_reset_domain(hive->reset_domain)) {
 					r = -ENOENT;

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

···
 	if (ret) {
 		dev_err(adev->dev, "XGMI: failed initializing kobject for xgmi hive\n");
 		kobject_put(&hive->kobj);
-		kfree(hive);
 		hive = NULL;
 		goto pro_end;
 	}
···
 				dev_err(adev->dev, "XGMI: failed initializing reset domain for xgmi hive\n");
 				ret = -ENOMEM;
 				kobject_put(&hive->kobj);
-				kfree(hive);
 				hive = NULL;
 				goto pro_end;
 			}