ALSA: scarlett2: Refactor scarlett2_config_save()

Use the new scarlett2_usb_activate_config() helper function rather
than preparing the request manually and calling scarlett2_usb().

Signed-off-by: Geoffrey D. Bennett <g@b4.vu>
Link: https://lore.kernel.org/r/bbc733dc081f311fb3167e81b15cd76324aa6307.1703444932.git.g@b4.vu


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