ALSA: hda - Make position_fix as generic callback

... and move most parts into hda_intel.c from the generic controller
code.  This is a clean up, and there should be no functional change by
this patch.

Now, struct azx obtains the generic callbacks for getting the position
and the delay.  As default NULL, posbuf is read.  These replace the
old position_fix[], and each is implemented as a callback.

Signed-off-by: Takashi Iwai <tiwai@suse.de>