timer: fix return value when failing devnode detection of ALSA Timer character device

timer: fix return value when failing devnode detection of ALSA Timer character device

When failing detecting devnode of ALSA Timer character device, the helper
function returns negative value to the callers. This is overlooked in the
previous code refactoring. It should return FALSE.

This bug brings the following compiler warnings:

../src/timer/query.c: In function ‘alsatimer_get_device_id_list’:
../src/timer/query.c:122:13: warning: ‘fd’ may be used uninitialized [-Wmaybe-uninitialized]
  122 |         if (ioctl(fd, SNDRV_TIMER_IOCTL_NEXT_DEVICE, &id) < 0) {
      |             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
../src/timer/query.c:109:9: note: ‘fd’ was declared here
  109 |     int fd;
      |         ^~

This commit fixes the bug.

Fixes: 487c67a62e99 ("timer: query: rewrite public API to return gboolean according to GNOME convention")
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>