VT1708 has no support for unsolicited events per jack-plug, the driver
implements the workq for polling the jack-detection. The mixer element
"Jack Detect" was supposed to control this behavior on/off, but this
doesn't work properly as is now. The workq is always started and the
HP automute is always enabled.
This patch fixes the jack-detect control behavior by triggering / stopping
the work appropriately at the state change. Also the work checks the
internal state to continue scheduling or not.
Cc: <stable@kernel.org> [v3.1]
Signed-off-by: Takashi Iwai <tiwai@suse.de>