ALSA: Use a define for the number of jack switch types

This is intended to facilitate the merge of the two jack detection
mechanisms.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

include/sound/jack.h

@@ -53,6 +53,9 @@ enum snd_jack_types {
 	SND_JACK_BTN_5		= 0x0200,
 };
 
+/* Keep in sync with definitions above */
+#define SND_JACK_SWITCH_TYPES 6
+
 struct snd_jack {
 	struct input_dev *input_dev;
 	int registered;