At the first time update_mute_led() gets called, if channels are already
muted, the temp value equals to led_value as 0, skipping the following
LED setting.

So set led_value to -1 as an uninitialized state, to update the correct
LED status at first time usage.

Fixes: 5d43001a ("ASoC: SOF: acpi led support for switch controls")
Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
Reviewed-by: Ranjani Sridharan <ranjani.sridharan@linux.intel.com>
Acked-by: Kai Vehmanen <kai.vehmanen@linux.intel.com>
Link: https://lore.kernel.org/r/20200430091139.7003-1-kai.heng.feng@canonical.comSigned-off-by: Mark Brown <broonie@kernel.org>