ALSA: scarlett2: Add correct product series name to messages

This driver was originally developed for the Focusrite Scarlett Gen 2
series, but now also supports the Scarlett Gen 3 series, the
Clarett 8Pre USB, and the Clarett+ 8Pre. The messages output by the
driver on initialisation and error include the identifying text
"Scarlett Gen 2/3", but this is no longer accurate, and writing
"Scarlett Gen 2/3/Clarett USB/Clarett+" would be unwieldy.

Add series_name field to the scarlett2_device_entry struct so that
concise and accurate messages can be output.

Signed-off-by: Geoffrey D. Bennett <g@b4.vu>
Link: https://lore.kernel.org/r/3774b9d35bf1fbdd6fdad9f3f4f97e9b82ac76bf.1694705811.git.g@b4.vu
Signed-off-by: Takashi Iwai <tiwai@suse.de>