ALSA: hda/hdmi: Register with vga_switcheroo on Dual GPU Macbooks

ALSA: hda/hdmi: Register with vga_switcheroo on Dual GPU Macbooks

Commit 586bc4aab878 ("ALSA: hda/hdmi - fix vgaswitcheroo detection for
AMD") caused only AMD gpu's with PX to have their audio component register
with vga_switcheroo. This meant that Apple Macbooks with apple-gmux as the
gpu switcher no longer had the audio client registering, so when the gpu is
powered off by vga_switcheroo snd_hda_intel is unaware that it should have
suspended the device:

amdgpu: switched off
snd_hda_intel 0000:03:00.1:
    Unable to change power state from D3hot to D0, device inaccessible
snd_hda_intel 0000:03:00.1: CORB reset timeout#2, CORBRP = 65535

To resolve this, we use apple_gmux_detect() and register a
vga_switcheroo audio client when apple-gmux is detected.

Fixes: 586bc4aab878 ("ALSA: hda/hdmi - fix vgaswitcheroo detection for AMD")
Link: https://lore.kernel.org/all/[email protected]/
Signed-off-by: Orlando Chamberlain <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Takashi Iwai <[email protected]>