Revert "netfilter: rpfilter/fib: Populate flowic_l3mdev field"

This reverts commit d98558fe which is
commit acc641ab upstream.

It breaks the Android kernel abi and can be brought back in the future
in an abi-safe way if it is really needed.

Bug: 161946584
Change-Id: Id5c8d6759b996ff84343f011ed32aec76d8b7260
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>