USB: usb-storage: merge DPCM support into SDDR09

The DPCM subdriver is a little peculiar, in that it's meant to support
devices where LUN 0 is Compact Flash and uses the CB transport whereas
LUN 1 is SmartMedia and uses the SDDR09 transport.  Thus DPCM isn't
really a transport in itself; it's more like a demultiplexer.

Much of the DPCM code is part of the SDDR09 subdriver already, and the
remaining part is fairly small.  This patch (as1182) moves that extra
piece into sddr09.c, thereby eliminating dpcm.c.  Also eliminated is
the Kconfig entry for DPCM support; it is now listed as part of the
SDDR09 entry.

In order to make sure that the semantics are the same as before, each
unusual_devs entry for DPCM is now present twice: once with DPCM
support if SDDR09 is configured (as before), and once with the
SINGLE_LUN flag and CB support otherwise.

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>