ALSA: HDA: Unify HDMI hotplug handling.

This change unifies the initial handling of a pin's state with the code to
update a pin's state after a hotplug (unsolicited response) event. The
initial probing, and all updates, are now routed through hdmi_present_sense.

The stored PD and ELDV status is now always derived from GetPinSense verb
execution, and not from the data in the unsolicited response. This means:

a) The WAR for NVIDIA codec's UR.PD values ("old_pin_detect") can be
   removed, since this only affected the no-longer-used unsolicited
   response payload.

b) In turn, this means that most NVIDIA codecs can simply use
   patch_generic_hdmi instead of having a custom variant just to set
   old_pin_detect.

c) When PD && ELDV becomes true, no extra verbs are executed, because the
   GetPinSense that was previously executed by snd_hdmi_get_eld (really,
   hdmi_eld_valid) has simply moved into hdmi_present_sense.

d) When PD && ELDV becomes false, there is a single extra GetPinSense verb
   executed for codecs where old_pin_detect wasn't set, i.e. some NVIDIA,
   and all ATI/AMD and Intel codecs. I doubt this will be a performance
   issue.

The new unified code in hdmi_present_sense also ensures that eld->eld_valid
is not set unless eld->monitor_present is also set. This protects against
potential invalid combinations of PD and ELDV received from HW, and
transitively from a graphics driver.

Also, print the derived PD/ELDV bits from hdmi_present_sense so the kernel
log always displays the actual state stored, which will differ from the
values in the unsolicited response for NVIDIA HW where old_pin_detect was
previously set.

Finally, a couple of small tweaks originally by Takashi:

* Clear the ELD content to zero before reading it, so that if it's not
  read (i.e. when !(PD && ELDV)) it's in a known state.

* Don't show ELD fields in /proc ELD files when the ELD isn't valid.

The only possibility I can see for regression here is a codec where the
GetPinSense verb returns incorrect data. However, we're already exposed
to that, since that data is used (a) from hdmi_add_pin to set up the
initial pin state, and (b) within snd_hda_input_jack_report to query
a pin's presence value. As such, I don't believe any HW has bugs here.

Includes-changes-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Stephen Warren <swarren@nvidia.com>
Acked-by: Wu Fengguang <fengguang.wu@intel.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

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