misc whitespace cosmetics
Avoid a number of pointer dereferences inside av_qsv_stage_clean().
Avoid unnecessary pointer dereferences in av_qsv_pipe_list_create().
Avoid unnecessary pointer dereference in av_qsv_list_close().
Avoid unnecessary pointer dereference in av_qsv_pipe_list_clean().
Avoid unnecessary pointer dereference in av_qsv_add_stage().
Avoid unnecessary pointer dereference in av_qsv_flush_stages().
Avoid unnecessary pointer dereference inside av_qsv_flush_stages().