ASoC: sgtl5000: Fix noise on shutdown/remove

ASoC: sgtl5000: Fix noise on shutdown/remove

Put the SGTL5000 in a silent/safe state on shutdown/remove, this is
required since the SGTL5000 produces a constant noise on its output
after it is configured and its clock is removed. Without this change
this is happening every time the module is unbound/removed or from
reboot till the clock is enabled again.

The issue was experienced on both a Toradex Colibri/Apalis iMX6, but can
be easily reproduced everywhere just playing something on the codec and
after that removing/unbinding the driver.

Fixes: b394de4e240e ("ASoC: Add Freescale SGTL5000 codec support")
Signed-off-by: Francesco Dolcini <francesco.dolcini@toradex.com>
Reviewed-by: Fabio Estevam <festevam@denx.de>
Link: https://lore.kernel.org/r/20220624101301.441314-1-francesco.dolcini@toradex.com
Signed-off-by: Mark Brown <broonie@kernel.org>