ALSA: hda - fix beep tone calculation for IDT/STAC codecs

In the beep tone calculation for IDT/STAC codecs, lower numbers correspond
to higher frequencies and vice versa.  The current code has this backwards,
resulting in beep frequencies which are way too high (and sound bad on
tinny laptop speakers, resulting in complaints).

[Also added hz <= 0 check by tiwai]

Signed-off-by: Paul Vojta <vojta@math.berkeley.edu>
Signed-off-by: Takashi Iwai <tiwai@suse.de>