Fix the Cressi Nepto filter function

The model number in the bluetooth device name appears to be encoded as a
hexadecimal number instead of a decimal number (e.g. a_xxxx vs 10_xxxx
for the Nepto).

Author: jefdriesen

src/descriptor.c

@@ -612,7 +612,7 @@ dc_match_cressi (const void *key, const void *value)
 
 	char prefix[16] = {0};
 
-	dc_platform_snprintf(prefix, sizeof(prefix), "%u_", model);
+	dc_platform_snprintf(prefix, sizeof(prefix), "%x_", model);
 
 	const char *p = prefix;