msm: ipa3: put ecm default as vlan in auto config

Made the change to put ecm as default in vlan mode
on auto configuration to resolve the issue where
usb connects to IPA faster than ipa-driver getting
vlan info from user-space.

Change-Id: I83d876e555e06eba762d98394e155df9b9797820
Signed-off-by: Skylar Chang <chiaweic@codeaurora.org>