usb: gadget: Select RNDIS over ethernet as default class

Win7/Win10 host is using NDIS 6.0 driver for RNDIS over ethernet and
NDIS5.0 for RNDIS over wireless controller or active sync.
NDIS 6.0 is performing better than NDIS5 with respect to performance
and data stalls. Hence, by default use RNDIS over ethernet class for
gsi driver which loads NDIS6 driver on windows.

Change-Id: I52f7a91dcb89be6c5b01c3efaf791375a50237fe
Signed-off-by: Vamsi Krishna Samavedam <vskrishn@codeaurora.org>
Signed-off-by: Hemant Kumar <hemantk@codeaurora.org>