ALSA: scarlett2: Add missing sentinel initializer field

ALSA: scarlett2: Add missing sentinel initializer field

A "-Wmissing-field-initializers" warning was emitted when compiling the
module using the W=2 option. There is a sentinel initializer field
missing in the end of scarlett2_devices[]. Tested using a
Scarlett Solo 4th gen.

Fixes: d98cc489029d ("ALSA: scarlett2: Move USB IDs out from device_info struct")
Signed-off-by: Panagiotis Petrakopoulos <npetrakopoulos2003@gmail.com>
Link: https://patch.msgid.link/20260405222548.8903-1-npetrakopoulos2003@gmail.com
Signed-off-by: Takashi Iwai <tiwai@suse.de>