[ALSA] Fix misuse of __list_add() in seq_ports.c

seq_ports.c::snd_seq_delete_all_ports() uses __list_add() to replace the
whole list entries.  This results in BUG() with recent FC5 kernel due to
a sanity check in __list_add().
The patch fixes this misue of __list_add() by using standard macros
instead (although a bit more code is needed).

Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Jaroslav Kysela <perex@suse.cz>