audio/hda: tweak timer adjust logic

We have some jitter in the audio timer call frequency and buffer sizes.
So it is rather pointless trying to be very exact, effect is a constant
up+down adjustment.  So adjust only in case we are off too much.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Message-id: 20180622111200.30561-4-kraxel@redhat.com