h264encode: check driver supports the RateControl control mode or not
h264encode: check driver supports the RateControl control mode or not

https://bugs.freedesktop.org/show_bug.cgi?id=76720

Signed-off-by: Xiang, Haihao <8d677183e5993577d4fa73a419b76987913292d6@intel.com>

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