USB: usb-storage: new "lockable" subclass 0x07

This patch (as1011) adds a #define for the newly-created Lockable
(i.e., password-protected) subclass 0x07 for USB mass-storage devices.
The private ISD200 entry (which had been mapped to subclass 0x07) is
moved to 0xf0, which is unlikely to conflict with any official
subclass designation.

The US_SC_MIN and US_SC_MAX constants aren't used anywhere, so the
patch removes them.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Cc: Matthew Dharm <mdharm-usb@one-eyed-alien.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>