libs: Change the parameter setting order when encode picture.

The order in gst_vaapi_enc_picture_encode when encoding one picture is not very correct. The misc parameters are set before the picture parameters. Some of the misc parameters such as ROI may change the current picture parameters. But the later setting of picture parameter will re-init all picture related parameters and clear the previous setting. The right order should be picture parameter first and then misc parameters.

Signed-off-by: He Junyan junyan.he@hotmail.com