Force it to use asynchronous playback.

Same quirk has already been added for Focusrite Scarlett Solo (2nd gen)
with a commit 46f5710f ("ALSA: usb-audio: Add quirk for Focusrite
Scarlett Solo").

This also seems to prevent regular clicks when playing at 44100Hz
on Scarlett 2i2 (2nd gen). I did not notice any side effects.

Moved both quirks to snd_usb_audioformat_attributes_quirk() as suggested.
Signed-off-by: Gregor Pintar <grpintar@gmail.com>
Reviewed-by: Alexander Tsoy <alexander@tsoy.me>
Link: https://lore.kernel.org/r/20200420214030.2361-1-grpintar@gmail.comSigned-off-by: Takashi Iwai <tiwai@suse.de>