ALSA: info: Fix leaks of child entries at snd_info_free_entry()

snd_info_free_entry() releases the all children nodes as well, but due
to the wrong timing of releasing the link, the children nodes may be
disconnected but left unreleased.  This patch fixes it by moving the
link free at the right position.  Also it eases list_for_each_entry()
without _safe option in snd_info_disconnect() because it no longer
frees the children nodes there.

Fixes: c560a679 ('ALSA: core: Remove child proc file elements recursively')
Signed-off-by: Takashi Iwai <tiwai@suse.de>