ASoC: imx-audio-rpmsg: Create rpmsg channel for MICFIL

Rpmsg channel for MICFIL can also be created through rpmsg name service
announcement. If this driver is probed, Cortex-A can access MICFIL
which is actually controlled by Cortex-M through rpmsg channel for
MICFIL. This driver also helps register ASoC platform device thus use
of PLATFORM_DEVID_AUTO macro in API can automatically create device for
each rpmsg channel.

Signed-off-by: Chancel Liu <chancel.liu@nxp.com>
Acked-by: Shengjiu Wang <shengjiu.wang@gmail.com>
Link: https://lore.kernel.org/r/20220930064441.2548505-3-chancel.liu@nxp.com


Signed-off-by: Mark Brown <broonie@kernel.org>