ALSA: usb-audio: fix uac2 clock source at terminal parser

ALSA: usb-audio: fix uac2 clock source at terminal parser

Since 8b3a087f7f65 ("ALSA: usb-audio: Unify virtual type units type to
UAC3 values") usb-audio is using UAC3_CLOCK_SOURCE instead of
bDescriptorSubtype, later refactored with e0ccdef9265 ("ALSA: usb-audio:
Clean up check_input_term()") into parse_term_uac2_clock_source().

This breaks the clock source selection for at least my
1397:0003 BEHRINGER International GmbH FCA610 Pro.

Fix by using UAC2_CLOCK_SOURCE in parse_term_uac2_clock_source().

Fixes: 8b3a087f7f65 ("ALSA: usb-audio: Unify virtual type units type to UAC3 values")
Signed-off-by: René Rebe <rene@exactco.de>
Link: https://patch.msgid.link/20251125.154149.1121389544970412061.rene@exactco.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>