ALSA: hda - Fix NULL dereference with CONFIG_SND_DYNAMIC_MINORS=n

commit 2ca320e294a738c9134a71b5029de05edbfc7aad upstream.

Without the dynamic minor assignment, HDMI codec may have less PCM
instances than the number of pins, which eventually leads to Oops.

Reported-by: Stratos Karafotis <stratosk@semaphore.gr>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>