Revert "net: rtnetlink: add msg kind names"

This reverts commit a8b1eeb9 which is
commit 12dc5c2c 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: I780457e01724f9a48db68aefe4cd71a6628174e0
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>