Rework the core usbatm code: minidrivers (i.e. drivers for particular
modems) now register themselves with the usbatm core, supplying methods
for binding/unbinding etc.  The design was inspired by usb-serial and
usbnet.  At the same time, more common code from the speedtch and
cxacru (patch 3/5) drivers was generalized and moved into the core.  The
transmission and reception parts have been unified and simplified.  Since
this is a major change and I don't like underscores in file names,
usb_atm.[ch] has been renamed usbatm.[ch].

Many thanks to Roman Kagan, who did a lot of the coding.
Signed-off-by: NDuncan Sands <baldrick@free.fr>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>