test/encode/avcenc: Add a parameter to set I/IP/IPB mode
test/encode/avcenc: Add a parameter to set I/IP/IPB mode

Signed-off-by: Hai Lan <hai.lan@intel.com

01org/libva-cros,01org/libva-cros,zzhhui/libva,01org/iotg-lin-gfx-libva,chenxianqin/vaapi-libva,pma1/libva,01org/libva-cros,01org/iotg-lin-gfx-libva,zzhhui/libva,chenxianqin/vaapi-libva,pma1/libva,chenxianqin/vaapi-libva,gbeauchesne/libva,zzhhui/libva,pma1/libva,gbeauchesne/libva,gbeauchesne/libva,01org/iotg-lin-gfx-libva