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: d98cc48902 ("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>

sound/usb/mixer_scarlett2.c

@@ -2262,7 +2262,7 @@ static const struct scarlett2_device_entry scarlett2_devices[] = {
 	{ USB_ID(0x1235, 0x820c), &clarett_8pre_info, "Clarett+" },
 
 	/* End of list */
-	{ 0, NULL },
+	{ 0, NULL, NULL },
 };
 
 /* get the starting port index number for a given port type/direction */