ALSA: hda - Add position_check op

This op will be used by hda_intel to do the position check.  Takashi
wisely suggested adding this before moving the interrupt handler to
common HDA code.  Having this callback prevents the need to move the
hda_intel specific delayed interrupt handling with the irq.

Signed-off-by: Dylan Reid <dgreid@chromium.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>