This patch adds a 'mtu' value to the Ip4Config and Ip6Config property of
a Bearer object, which indicates the value of the maximum transmission
unit for the established connection when such information is available
(e.g. via QMI_WDS_GET_RUNTIME_SETTINGS on a QMI modem or
MBIM_CID_IP_CONFIGURATION on a MBIM modem).
e4db8c5302