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

This reverts commit 5c6cb7ab 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: I2ad6d3d29b9937f0391d558e2e8de22d907a1829
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>