ALSA: usb-audio: scarlett2: Reformat scarlett2_config_items[]

Use designated initializers and merge lines in preparation for more
configuration items coming soon.

Signed-off-by: Geoffrey D. Bennett <g@b4.vu>
Link: https://lore.kernel.org/r/512d14eeb3571a266810c954d0f83140a3af7afc.1624294591.git.g@b4.vu


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