Enable ethernet data usage when FEATURE_USB_HOST is present

Ethernet is enabled when either FEATURE_ETHERNET *or* FEATURE_USB_HOST
is present. See ConnectivityService#deviceSupportsEthernet.

ConnectivityService#deviceSupportsEthernet should really be moved to
some commonly accessible location.

Test: TH
Change-Id: I497d99169248db7e5948b3a19134ab42e66d5b9b