arm64: defconfig: Enable CONFIG_SND_AUDIO_GRAPH_CARD

CONFIG_SND_AUDIO_GRAPH_CARD is needed to use HDMI sound with video

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>