USB: sierra: Fix id for Sierra Wireless MC8755 in new table

The new version of sierra.c has introduced tables for the 1 port and 3
port variants. The device id i added in my last patch needs to be added
to the 3 port table.

Signed-off-by: Jan Luebbe <jluebbe@lasnet.de>
Cc: Kevin Lloyd <linux@sierrawireless.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>