ALSA: hdspm - Fix default value in SNDRV_HDSPM_IOCTL_GET_LTC

Use enum hdspm_ltc_format's fps_30 (corresponds to 4) instead of 30,
Other case branches return 1, 2 or 3 respectively, so 30 obviously is
wrong.

Since SNDRV_HDSPM_IOCTL_GET_LTC had never been working due to a
copy&paste error in hdspm.h, this change doesn't break userspace.

Signed-off-by: Adrian Knoth <adi@drcomp.erfurt.thur.de>
Signed-off-by: Takashi Iwai <tiwai@suse.de>