ALSA: usb-audio: scarlett2: Remove repeated device info comments

Document the fields of struct scarlett2_device_info in the definition
of the struct, not in each instantiation.

Signed-off-by: Geoffrey D. Bennett <g@b4.vu>
Link: https://lore.kernel.org/r/3486e4d38973333d4ec38f32578c16a9f97bf6c8.1624294591.git.g@b4.vu


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