ixp4xx: fix Avila SoC audio driver compilation

ixp4xx: fix Avila SoC audio driver compilation

Upstream dropped the `dapm` member of `struct snd_soc_component`, requiring
users to access it using `snd_soc_codec_get_dapm()` instead so change the
driver code to do just that.

Fixes the following build error spotted by the buildbots:

      CC [M]  sound/soc/gw-avila/gw-avila.o
    sound/soc/gw-avila/gw-avila.c: In function 'avila_aic3x_init':
    sound/soc/gw-avila/gw-avila.c:104:44: error: 'struct snd_soc_codec' has no member named 'dapm'

Signed-off-by: Jo-Philipp Wich <jo@mein.io>