libusbhost: factor out frameworks descriptors -> byte[] code.

Sony needed to increase the limit for a UVC device with > 4KiB
descriptors, but there wasn't one clean place to do that. Tidy up, and
also go straight to *16KiB* which was the largest buffer any copy of
this code was using to date.

Test: treehugger
Change-Id: Ide41a217dcf4291a7d38836264f59e06967d9d91
diff --git a/libusbhost/usbhost_private.h b/libusbhost/usbhost_private.h
new file mode 100644
index 0000000..72d7938
--- /dev/null
+++ b/libusbhost/usbhost_private.h
@@ -0,0 +1,25 @@
+/*
+ * Copyright (C) 2022 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#pragma once
+
+#define LOG_TAG "usbhost"
+#include <log/log.h>
+
+// Somewhat arbitrary: Sony has reported needing more than 4KiB (but less
+// than 8KiB), and some frameworks code had 16KiB without any explanation,
+// so we went with the largest of those.
+#define MAX_DESCRIPTORS_LENGTH (16 * 1024)