Replace usb_set_debug() in utils by new group in LIBNFC_LOG_LEVEL

To use it: (NFC_LOG_PRIORITY_DEBUG * 2 ^ NFC_LOG_GROUP_LIBUSB)
LIBUSB_LOG_LEVEL=12288

utils/nfc-scan-device.c

@@ -38,12 +38,6 @@
 #  include "config.h"
 #endif // HAVE_CONFIG_H
 
-#ifdef HAVE_LIBUSB
-#  ifdef DEBUG
-#    include <usb.h>
-#  endif
-#endif
-
 #include <err.h>
 #include <stdio.h>
 #include <stddef.h>
@@ -101,12 +95,6 @@ main(int argc, const char *argv[])
   acLibnfcVersion = nfc_version();
   printf("%s uses libnfc %s\n", argv[0], acLibnfcVersion);
 
-#ifdef HAVE_LIBUSB
-#  ifdef DEBUG
-  usb_set_debug(4);
-#  endif
-#endif
-
   nfc_connstring connstrings[MAX_DEVICE_COUNT];
   size_t szDeviceFound = nfc_list_devices(context, connstrings, MAX_DEVICE_COUNT);