USB: allow usbstorage to have LUNS greater than 2Tb

Attached is a very small patch (several comment lines) and a one-line
coded change) that allows for USB storage devices that are larger than
2TB.

At the company where I work we need such support, and one of my
co-workers, Jane Liu, pointed out that SCSI low-layer drivers need to
specify what size CDBs they accept. After looking through the code it
became obvious that the current USB Storage code accepted the default of
12-byte CDBs, so I changed it to accept 16-byte CDBs. This allows our
device to work.

Signed-off-by: Richard Sharpe <rsharpe@richardsharpe.com>
Signed-off-by: Matthew Dharm <mdharm-usb@one-eyed-alien.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>