fel: Detach (and reattach on exit) the awusb kernel driver if loaded

fel.c

@@ -278,6 +278,7 @@ int main(int argc, char **argv)
 {
 	int rc;
 	libusb_device_handle *handle = NULL;
+	int iface_detached = -1;
 	rc = libusb_init(NULL);
 	assert(rc == 0);
 
@@ -301,6 +302,13 @@ int main(int argc, char **argv)
 		exit(1);
 	}
 	rc = libusb_claim_interface(handle, 0);
+#if defined(__linux__)
+	if (rc != LIBUSB_SUCCESS) {
+		libusb_detach_kernel_driver(handle, 0);
+		iface_detached = 0;
+		rc = libusb_claim_interface(handle, 0);
+	}
+#endif
 	assert(rc == 0);
 
 	while (argc > 1 ) {
@@ -345,5 +353,10 @@ int main(int argc, char **argv)
 		argv+=skip;
 	}
 
+#if defined(__linux__)
+	if (iface_detached >= 0)
+		libusb_attach_kernel_driver(handle, iface_detached);
+#endif
+
 	return 0;
 }