ALSA: usb-audio: scarlett2: Update initialisation sequence

The old initialisation code only works with Gen 2 devices. Replace it
with an initialisation sequence that works on both Gen 2 and Gen 3
devices.

Signed-off-by: Geoffrey D. Bennett <g@b4.vu>
Link: https://lore.kernel.org/r/6e5c4fedb74b813872f6a4b7fba30b6c471fa63a.1624294591.git.g@b4.vu


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