ALSA: aloop: Fix Oops while PM resume

snd-aloop driver has no proper PM implementation, thus the PM resume
may trigger Oops due to leftover timer instance.  This patch adds the
missing suspend/resume implementation.

Reported-and-tested-by: El boulangero <elboulangero@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>