This reworks the usb_serial_register_drivers() and
usb_serial_deregister_drivers() to not need a pointer to a struct
usb_driver anymore.  The usb_driver structure is now created dynamically
and registered and unregistered as needed.

This saves lines of code in each usb-serial driver.  All in-kernel users
of these functions were also fixed up at this time.  The pl2303 driver
was tested that everything worked properly.

Thanks for the idea to do this from Alan Stern.

Cc: Adhir Ramjiawan <adhirramjiawan0@gmail.com>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: Al Borchers <alborchers@steinerpoint.com>
Cc: Aleksey Babahin <tamerlan311@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andrew Worsley <amworsley@gmail.com>
Cc: Bart Hartgers <bart.hartgers@gmail.com>
Cc: Bill Pemberton <wfp5p@virginia.edu>
Cc: Dan Carpenter <error27@gmail.com>
Cc: Dan Williams <dcbw@redhat.com>
Cc: Donald Lee <donald@asix.com.tw>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Felipe Balbi <balbi@ti.com>
Cc: Gary Brubaker <xavyer@ix.netcom.com>
Cc: Jesper Juhl <jj@chaosbits.net>
Cc: Jiri Kosina <jkosina@suse.cz>
Cc: Johan Hovold <jhovold@gmail.com>
Cc: Julia Lawall <julia@diku.dk>
Cc: Kautuk Consul <consul.kautuk@gmail.com>
Cc: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Cc: Lonnie Mendez <dignome@gmail.com>
Cc: Matthias Bruestle and Harald Welte <support@reiner-sct.com>
Cc: Matthias Urlichs <smurf@smurf.noris.de>
Cc: Mauro Carvalho Chehab <mchehab@redhat.com>
Cc: Michal Sroczynski <msroczyn@gmail.com>
Cc: "Michał Wróbel" <michal.wrobel@flytronic.pl>
Cc: Oliver Neukum <oliver@neukum.name>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Peter Berger <pberger@brimson.com>
Cc: Preston Fick <preston.fick@silabs.com>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
Cc: Rigbert Hamisch <rigbert@gmx.de>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Simon Arlott <simon@fire.lp0.eu>
Cc: Support Department <support@connecttech.com>
Cc: Thomas Tuttle <ttuttle@chromium.org>
Cc: Uwe Bonnes <bon@elektron.ikp.physik.tu-darmstadt.de>
Cc: Wang YanQing <Udknight@gmail.com>
Cc: William Greathouse <wgreathouse@smva.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>