drm/amdkfd: Fix a bug when calculating save_area_used_size

workgroup context data writes from m->cp_hqd_cntl_stack_size, so we
should deduct it when calculating the used size.

Signed-off-by: Yong Zhao <Yong.Zhao@amd.com>
Reviewed-by: Felix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdkfd/kfd_mqd_manager_v9.c

@@ -302,7 +302,8 @@ static int get_wave_state(struct mqd_manager *mm, void *mqd,
 
 	*ctl_stack_used_size = m->cp_hqd_cntl_stack_size -
 		m->cp_hqd_cntl_stack_offset;
-	*save_area_used_size = m->cp_hqd_wg_state_offset;
+	*save_area_used_size = m->cp_hqd_wg_state_offset -
+		m->cp_hqd_cntl_stack_size;
 
 	if (copy_to_user(ctl_stack, mqd_ctl_stack, m->cp_hqd_cntl_stack_size))
 		return -EFAULT;