drm/amdgpu: handle amdgpu_cgs_create_device() errors in amd_powerplay_create()

Add error handling to propagate amdgpu_cgs_create_device() failures
to the caller. When amdgpu_cgs_create_device() fails, release hwmgr
and return -ENOMEM to prevent null pointer dereference.

[v1]->[v2]: Change error code from -EINVAL to -ENOMEM. Free hwmgr.

Signed-off-by: Wentao Liang <vulab@iscas.ac.cn>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

Author: ISCAS-Vulab

drivers/gpu/drm/amd/pm/powerplay/amd_powerplay.c

@@ -51,6 +51,11 @@ static int amd_powerplay_create(struct amdgpu_device *adev)
 	hwmgr->adev = adev;
 	hwmgr->not_vf = !amdgpu_sriov_vf(adev);
 	hwmgr->device = amdgpu_cgs_create_device(adev);
+	if (!hwmgr->device) {
+		kfree(hwmgr);
+		return -ENOMEM;
+	}
+
 	mutex_init(&hwmgr->msg_lock);
 	hwmgr->chip_family = adev->family;
 	hwmgr->chip_id = adev->asic_type;