ALSA: hda - allow a codec to define its own depop delay time

This patch adds 'depop_delay' to struct hda_codec, to indicate a depop delay
time in ms when power-down, in function set_power_state() to D3.

Default value is -1, for a default delay time.
Machine fixup can set a suitable value according to the codec chip and HW audio
design.

Signed-off-by: Mengdong Lin <mengdong.lin@intel.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>