ASoC: rsnd: call missing snd_ctl_remove()

Current Renesas R-Car sound driver is using snd_ctl_xxx()
functions, but it didn't call snd_ctl free_one() / snd_ctl_remove().
This patch call these functions.

Reported-by: Nguyen Viet Dung <nv-dung@jinso.co.jp>
Reported-by: Bui Duc Phuc <bd-phuc@jinso.co.jp>
Reported-by: Cao Minh Hiep <cm-hiep@jinso.co.jp>
Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Mark Brown <broonie@kernel.org>