ALSA: led: Use restricted type for iface assignment

Fix a sparse warning that complains about the inconsistent type
assignment for iface, which is a restricted type of
snd_ctl_elem_iface_t.

Fixes: a135dfb5 ("ALSA: led control - add sysfs kcontrol LED marking layer")
Reported-by: kernel test robot <lkp@intel.com>
Reviewed-by: Jaroslav Kysela <perex@perex.cz>
Link: https://lore.kernel.org/r/202111201028.xduVYgH5-lkp@intel.com
Link: https://lore.kernel.org/r/20211123170247.2962-1-tiwai@suse.deSigned-off-by: Takashi Iwai <tiwai@suse.de>

sound/core/control_led.c

@@ -509,7 +509,7 @@ static char *parse_string(char *s, char *val, size_t val_size)
 	return s;
 }
 
-static char *parse_iface(char *s, unsigned int *val)
+static char *parse_iface(char *s, snd_ctl_elem_iface_t *val)
 {
 	if (!strncasecmp(s, "card", 4))
 		*val = SNDRV_CTL_ELEM_IFACE_CARD;