ALSA: jack: Add dummy snd_jack_set_key() definition

For fixing a build error with CONFIG_SND_JACK=n
  sound/soc/codecs/ts3a227e.c:223:2: error: implicit declaration of function ‘snd_jack_set_key’ [-Werror=implicit-function-declaration]
Signed-off-by: Takashi Iwai <tiwai@suse.de>

include/sound/jack.h

@@ -105,6 +105,13 @@ static inline void snd_jack_set_parent(struct snd_jack *jack,
 {
 }
 
+static inline int snd_jack_set_key(struct snd_jack *jack,
+				   enum snd_jack_types type,
+				   int keytype)
+{
+	return 0;
+}
+
 static inline void snd_jack_report(struct snd_jack *jack, int status)
 {
 }