USB: CDC-ACM quirk for MTK GPS

This patch adds a device quirk for a MediaTek Inc GPS chipset. The
device implements USB CDC ACM, but is missing the union descriptor, so
the ACM class driver fails to probe the device.

I've tested this patch with an iBlue A+ GPS which uses this chipset
and using kernel 2.6.28-rc9.

Signed-off-by: Andrew Lunn, <andrew@lunn.ch>
Acked-by: Oliver Neukum <oneukum@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>