ALSA: scarlett2: Add Focusrite Clarett+ 8Pre support

ALSA: scarlett2: Add Focusrite Clarett+ 8Pre support

The Focusrite Clarett+ 8Pre uses the same protocol as the Scarlett Gen
2 and Gen 3 product range. This patch adds support for the Clarett+
8Pre by adding appropriate entries to the scarlett2 driver.

The Clarett+ 2Pre and 4Pre, and the Clarett USB product line
presumably use the same protocol as well, so support for them can
easily be added if someone can test.

Signed-off-by: Christian Colglazier <christian@cacolglazier.com>
Signed-off-by: Geoffrey D. Bennett <g@b4.vu>
Link: https://lore.kernel.org/r/20220809043241.GA2749152@m.b4.vu
Signed-off-by: Takashi Iwai <tiwai@suse.de>