usb: remove libusual

The "Low Performance USB Block driver" has been removed which a user of
libusual. Now we have only the usb-storage driver as the only driver in
tree. This makes libusual needless.
This patch removes libusal, fixes up all users. The usual-table is now
linked into usb-storage.
usb_usual.h remains in public include directory because some staging
users seem to need it.

Signed-off-by: Sebastian Andrzej Siewior <sebastian@breakpoint.cc>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>