ANDROID: restore abi breakage in usbnet.h

Commit de658a195ee2 ("net: usb: cdc_ncm: don't spew notifications") that
showed up in 5.4.125 added some new fields to struct usbnet.  "Restore"
the abi by using our pre-allocated padding as this change needs to stay
in the kernel for a set of common devices that it fixes problems for.

Bug: 161946584
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
Change-Id: I9383db108bf18a73e5cd838acf37917e82ba76c2