ASoC: meson: axg: extract sound card utils

[ Upstream commit aa9c3b7273a58b5d9b2c1161b76b5fc8ea8c159b ]

This prepares the addition of the GX SoC family sound card driver.
The GX sound card, while slightly different, will be similar to the
AXG one. The purpose of this change is to share the utils common to
both sound card driver.

Signed-off-by: Jerome Brunet <jbrunet@baylibre.com>
Link: https://lore.kernel.org/r/20200213155159.3235792-8-jbrunet@baylibre.com


Signed-off-by: Mark Brown <broonie@kernel.org>
Stable-dep-of: 4f9a71435953 ("ASoC: meson: axg-card: fix 'use-after-free'")
Signed-off-by: Sasha Levin <sashal@kernel.org>