ASoC: SOF: imx: fix reverse CONFIG_SND_SOC_SOF_OF dependency

ASoC: SOF: imx: fix reverse CONFIG_SND_SOC_SOF_OF dependency

updated solution to the problem reported with randconfig:

CONFIG_SND_SOC_SOF_IMX depends on CONFIG_SND_SOC_SOF, but is in
turn referenced by the sof-of-dev driver. This creates a reverse
dependency that manifests in a link error when CONFIG_SND_SOC_SOF_OF
is built-in but CONFIG_SND_SOC_SOF_IMX=m:

sound/soc/sof/sof-of-dev.o:(.data+0x118): undefined reference to `sof_imx8_ops'

use def_trisate to propagate the right settings without select.

Fixes: 912f9055b199 ("ASoC: SOF: imx8: Fix COMPILE_TEST error")
Fixes: f8612cb94e5f ("ASoC: SOF: imx: Add i.MX8 HW support")
Suggested-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Link: https://lore.kernel.org/r/20191101173045.27099-6-pierre-louis.bossart@linux.intel.com
Signed-off-by: Mark Brown <broonie@kernel.org>