MLK-21507 VPU Decoder: kernel panic if seek when video playing

MLK-21507 VPU Decoder: kernel panic if seek when video playing

    The same buffer prepend to the list twice at
    'VID_API_EVENT_REL_FRAME_BUFF'event and vpu_buf_queue()
    cause list form a dead cycle.
    Add an verification before prepend to list at vpu_buf_queue().

Unable to handle kernel paging request at virtual address dead000000000100
[<ffff000008bce7f4>] wait_right_buffer+0x60/0xac
[<ffff000008bd28f0>] vpu_api_event_handler+0xc64/0x1990
[<ffff000008bd3704>] vpu_msg_instance_work+0xe8/0x12c
[<ffff0000080f8518>] process_one_work+0x140/0x3f8
[<ffff0000080f8908>] worker_thread+0x138/0x3e4
[<ffff0000080fed70>] kthread+0x104/0x130
[<ffff000008085064>] ret_from_fork+0x10/0x18

Signed-off-by: Shijie Qin <shijie.qin@nxp.com>