usb: create common header virtual root hub descriptors

Many USB host controller drivers contain almost identical copies of the
same virtual root hub descriptors. Put these into a common file to avoid
duplication.

Note that there were some very minor differences between the descriptors
in the various files, such as:

- USB 1.0 vs. USB 1.1
- Manufacturer/Device ID
- Max packet size
- String content

I assume these aren't relevant.

Cc: Thomas Lange <thomas@corelatus.se>
Cc: Shinya Kuribayashi <skuribay@pobox.com>
Cc: Gary Jennejohn <garyj@denx.de>
Cc: Wolfgang Denk <wd@denx.de>
Cc: Eric Millbrandt <emillbrandt@coldhaus.com>
Cc: Pierre Aubert <p.aubert@staubli.com>
Cc: Stefan Roese <sr@denx.de>
Cc: Daniel Hellstrom <daniel@gaisler.com>
Cc: Denis Peter <d.peter@mpl.ch>
Cc: Rodolfo Giometti <giometti@linux.it>
Cc: Zhang Wei <wei.zhang@freescale.com>
Cc: Mateusz Zalega <m.zalega@samsung.com>
Cc: Remy Bohmer <linux@bohmer.net>
Cc: Markus Klotzbuecher <mk@denx.de>
Cc: Minkyu Kang <mk7.kang@samsung.com>
Cc: Gary Jennejohn <garyj@denx.de>
Cc: C Nauman <cnauman@diagraph.com>
Cc: David Müller <d.mueller@elsoft.ch>
Cc: Yoshihiro Shimoda <shimoda.yoshihiro@renesas.com>
Cc: Nobuhiro Iwamatsu <iwamatsu@nigauri.org>
Cc: Thomas Abraham <t-abraham@ti.com>
Cc: Tom Rini <trini@ti.com>
Cc: Andrew Murray <amurray@embedded-bits.co.uk>
Cc: Matej Frančeškin <matej.franceskin@comtrade.com>
Cc: Cliff Cai <cliff.cai@analog.com>
Cc: Bryan Wu <cooloney@gmail.com>
Signed-off-by: Stephen Warren <swarren@wwwdotorg.org>