ALSA: hda: fix possible NULL dereference

ALSA: hda: fix possible NULL dereference

commit c7e69ae6b4ff49edf50180c0a32f3dd9d7967e31 upstream.

After a for-loop was replaced by list_for_each_entry, see
Commit bbbc7e8502c9 ("ALSA: hda - Allocate hda_pcm objects dynamically"),
Commit 751e2216899c ("ALSA: hda: fix possible null dereference"),
a possible NULL pointer dereference has been introduced; this patch adds
the NULL check on pcm->pcm, while leaving a potentially superfluous
check on pcm itself untouched.

Signed-off-by: Markus Osterhoff <linux-kernel@k-raum.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>