[PATCH] USBATM: xusbatm rewrite

The xusbatm driver is for otherwise unsupported modems.
All it does is grab hold of a user-specified set of
interfaces - the generic usbatm core methods (hopefully)
do the rest.  As Aurelio Arroyo discovered when he tried
to use xusbatm (big mistake!), the interface grabbing logic
was completely borked.  Here is a rewrite that works.

Signed-off-by:	Duncan Sands <baldrick@free.fr>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>