UBUNTU: [Config] Add CONFIG_USB_NET_CDC_SUBSET_ENABLE=m

BugLink: http://bugs.launchpad.net/bugs/1756866

New config option which was added by upstream stable commit:
  f3bb2376: "USB: cdc_subset: only build when one driver is enabled"
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

debian.master/config/config.common.ubuntu

@@ -8383,6 +8383,7 @@ CONFIG_USB_NET_CDC_EEM=m
 CONFIG_USB_NET_CDC_MBIM=m
 CONFIG_USB_NET_CDC_NCM=m
 CONFIG_USB_NET_CDC_SUBSET=m
+CONFIG_USB_NET_CDC_SUBSET_ENABLE=m
 CONFIG_USB_NET_CH9200=m
 CONFIG_USB_NET_CX82310_ETH=m
 CONFIG_USB_NET_DM9601=m