kcontrol->private_value is being kfree'd after kcontrol has been freed
(in previous call to snd_ctl_remove).  Instead, fix this by kfreeing
the private_value before kcontrol.

CoverityScan CID#1388311 "Read from pointer after free"

Fixes: eea3dd4f ("ASoC: topology: Only free TLV for volume mixers of a widget")
Signed-off-by: NColin Ian King <colin.king@canonical.com>
Signed-off-by: NMark Brown <broonie@kernel.org>