MLK-22314-3 VPU Decoder: modify show performance measure

MLK-22314-3 VPU Decoder: modify show performance measure

1. start timer from open device;
2. add the interval from open device to feed first data and to
   send start cmd;
3. In order to reduce the time deviation of print log, use
   device_attribute file to show performance info.

Signed-off-by: Shijie Qin <shijie.qin@nxp.com>
Reviewed-by: ming_qian <ming.qian@nxp.com>