ALSA: usb-audio: Use correct sub-type for UAC3 feature unit validation

The entry of the validators table for UAC3 feature unit is defined
with a wrong sub-type UAC_FEATURE (= 0x06) while it should have been
UAC3_FEATURE (= 0x07).  This patch corrects the entry value.

Fixes: 57f87706 ("ALSA: usb-audio: More validations of descriptor units")
Link: https://patch.msgid.link/20250821150835.8894-1-tiwai@suse.de


Signed-off-by: Takashi Iwai <tiwai@suse.de>