USB: atm: usbatm: fix up debug printing code

If VERBOSE_DEBUG was enabled, lots of build errors happend (obviously no
one uses this mode.)  So fix that up, and get rid of the dbg() call, and
use dev_dbg() like the rest of the driver does.

Cc: Duncan Sands <duncan.sands@free.fr>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>