ALSA: hdspm: Fix zero-division

HDSPM driver contains a code issuing zero-division potentially in
system sample rate ctl code.  This patch fixes it by not processing
a zero or invalid rate value as a divisor, as well as excluding the
invalid value to be passed via the given ctl element.

Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>