ALSA: usb-audio: Update UMP group attributes for GTB blocks, too

When a FB is created from a GTB instead of UMP FB Info inquiry, we
missed the update of the corresponding UMP Group attributes.
Export the call of updater and let it be called from the USB driver.

Fixes: 0642a3c5 ("ALSA: ump: Update substream name from assigned FB names")
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Link: https://patch.msgid.link/20240807092303.1935-5-tiwai@suse.de