ALSA: usb-audio: Add QUIRK_FLAG_MIXER_GET_CUR_BROKEN for Logitech PRO X 2 LIGHTSPEED

ALSA: usb-audio: Add QUIRK_FLAG_MIXER_GET_CUR_BROKEN for Logitech PRO X 2 LIGHTSPEED

The UAC mixer of the Logitech PRO X 2 LIGHTSPEED has broken mixer
GET_CUR behavior but otherwise works fine.

Add a quirk table entry matching VID/PID=0x046d/0x0af7 and apply the
MIXER_GET_CUR_BROKEN quirk flag to make the mixer usable again.

Quirky device sample (after applying the quirk flag):

  usb 3-2.1: New USB device found, idVendor=046d, idProduct=0af7, bcdDevice= 1.00
  usb 3-2.1: New USB device strings: Mfr=1, Product=2, SerialNumber=3
  usb 3-2.1: Product: PRO X 2 LIGHTSPEED
  usb 3-2.1: Manufacturer: Logitech
  usb 3-2.1: SerialNumber: 0000000000000000
  usb 3-2.1: 2:0: broken mixer GET_CUR (-18944/0/256 => -2662)
  usb 3-2.1: 6:0: broken mixer GET_CUR (-18944/0/256 => 0)

Fixes: 86aa1ea1f15c ("ALSA: usb-audio: Do not expose sticky mixers")
Suggested-by: Brian van den Berg <faxuser@proton.me>
Reported-by: Brian van den Berg <faxuser@proton.me>
Link: https://lore.kernel.org/all/370007e6-b73b-4bfc-8410-a860781c7ad7@proton.me/
Signed-off-by: Rong Zhang <i@rong.moe>
Link: https://patch.msgid.link/20260731-uac-lg-pro-x-2-ls-v1-1-268eaefe66ab@rong.moe
Signed-off-by: Takashi Iwai <tiwai@suse.de>