ALSA: hda - hdmi: introduce patch_nvhdmi()

(This is a backport of *part* of upstream 611885bc963a "ALSA: hda -
hdmi: Disallow unsupported 2ch remapping on NVIDIA codecs" to stable
3.10 through 3.12. Later stable already contain all of the original
patch.)

Mainline commit 611885bc963a "ALSA: hda - hdmi: Disallow unsupported 2ch
remapping on NVIDIA codecs" introduces function patch_nvhdmi(). That
function is edited by 75fae117a5db "ALSA: hda/hdmi - allow PIN_OUT to be
dynamically enabled". In order to backport the PIN_OUT patch, I am first
back-porting just the addition of function patch_nvhdmi(), so that the
conflicts applying the PIN_OUT patch are simplified.

Ideally, one might backport all of 611885bc963a. However, that commit
doesn't apply to stable kernels, since it relies on a chain of other
patches which implement new features.

Signed-off-by: Anssi Hannula <anssi.hannula@iki.fi>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
[swarren, extracted just a small part of the original patch]
Signed-off-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>