drm/amdkfd: remove set but not used variable 'pdd'

Fixes gcc '-Wunused-but-set-variable' warning:

drivers/gpu/drm/amd/amdgpu/../amdkfd/kfd_process.c: In function restore_process_worker:
drivers/gpu/drm/amd/amdgpu/../amdkfd/kfd_process.c:949:29: warning:
 variable pdd set but not used [-Wunused-but-set-variable]

It is not used since
commit 5b87245f ("drm/amdkfd: Simplify kfd2kgd interface")
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdkfd/kfd_process.c

@@ -1044,7 +1044,6 @@ static void restore_process_worker(struct work_struct *work)
 {
 	struct delayed_work *dwork;
 	struct kfd_process *p;
-	struct kfd_process_device *pdd;
 	int ret = 0;
 
 	dwork = to_delayed_work(work);
@@ -1053,16 +1052,6 @@ static void restore_process_worker(struct work_struct *work)
 	 * lifetime of this thread, kfd_process p will be valid
 	 */
 	p = container_of(dwork, struct kfd_process, restore_work);
-
-	/* Call restore_process_bos on the first KGD device. This function
-	 * takes care of restoring the whole process including other devices.
-	 * Restore can fail if enough memory is not available. If so,
-	 * reschedule again.
-	 */
-	pdd = list_first_entry(&p->per_device_data,
-			       struct kfd_process_device,
-			       per_device_list);
-
 	pr_debug("Started restoring pasid %d\n", p->pasid);
 
 	/* Setting last_restore_timestamp before successful restoration.