ALSA: scarlett2: Refactor scarlett2_usb_set_config()

Pull out common code from scarlett2_usb_set_config() and create
scarlett2_usb_set_data() and scarlett2_usb_activate_config().

Signed-off-by: Geoffrey D. Bennett <g@b4.vu>
Link: https://lore.kernel.org/r/257eca0b07708339133f916930e388057d116eb8.1703444932.git.g@b4.vu


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