overlay_qsv hard coded to use nv12 as output format. Now use the format
of the first input to set output format.

For detailed information of supported format on different platform,
please see the "composition" rows in "Video Processing Features" at
below link:
https://www.intel.com/content/www/us/en/develop/documentation/media-capabilities-of-intel-hardware/top.htmlSigned-off-by: Wenbin Chen <wenbin.chen@intel.com>
Signed-off-by: Haihao Xiang <haihao.xiang@intel.com>