[PATCH] USB: cdc-acm: add a new special case for modems with buggy firmware

this fixes the "duplicated text" bug. There's a modem that cannot cope
with large transfers and more than one urb in flight. This patch adds a
special case to the driver.

Signed-off-by: Oliver Neukum <oliver@neukum.name>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>