ASoC: fsl: fix SND_SOC_IMX_RPMSG dependency

ASoC: fsl: fix SND_SOC_IMX_RPMSG dependency

Kconfig produces a warning with SND_SOC_FSL_RPMSG=y and SND_IMX_SOC=m:

WARNING: unmet direct dependencies detected for SND_SOC_IMX_RPMSG
  Depends on [m]: SOUND [=y] && !UML && SND [=y] && SND_SOC [=y] && SND_IMX_SOC [=m] && RPMSG [=y]
  Selected by [y]:
  - SND_SOC_FSL_RPMSG [=y] && SOUND [=y] && !UML && SND [=y] && SND_SOC [=y] && COMMON_CLK [=y] && RPMSG [=y] && SND_IMX_SOC [=m]!=n

Add a dependency to prevent this configuration.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Shengjiu Wang <shengjiu.wang@gmail.com>
Link: https://lore.kernel.org/r/20210514213118.630427-1-arnd@kernel.org
Signed-off-by: Mark Brown <broonie@kernel.org>