ASoC: wm_adsp: Don't generate kcontrols without READ flags

ASoC: wm_adsp: Don't generate kcontrols without READ flags

BugLink: https://bugs.launchpad.net/bugs/1852111
[ Upstream commit 3ae7359c0e39f42a96284d6798fc669acff38140 ]

User space always expects to be able to read ALSA controls, so ensure
no kcontrols are generated without an appropriate READ flag. In the case
of a read of such a control zeros will be returned.

Signed-off-by: Stuart Henderson <stuarth@opensource.cirrus.com>
Signed-off-by: Charles Keepax <ckeepax@opensource.cirrus.com>
Link: https://lore.kernel.org/r/20191002084240.21589-1-ckeepax@opensource.cirrus.com
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Connor Kuehl <connor.kuehl@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>