UBI: add a commentary about allocating VID header buffer on stack

	size_t written;

	size_t written;

	loff_t addr;

	loff_t addr;

	uint32_t data = 0;

	uint32_t data = 0;

	/*

	 * Note, we cannot generally define VID header buffers on stack,

	 * because of the way we deal with these buffers (see the header

	 * comment in this file). But we know this is a NOR-specific piece of

	 * code, so we can do this. But yes, this is error-prone and we should

	 * (pre-)allocate VID header buffer instead.

	 */

	struct ubi_vid_hdr vid_hdr;

	struct ubi_vid_hdr vid_hdr;

	/*

	/*