USB: Support for the ET502HS HDSPA modem

The attached patch allows to bypass the ZeroCD mechanism for the ET502HS
HDSPA modem, so that it can be mounted as a network device.

Signed-off-by: Mauro Andreolini <andreoli@weblab.ing.unimo.it>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>