Revert "net: dev: Convert sa_data to flexible array in struct sockaddr"

This reverts commit f6ce9056 which is
commit b5f0de6d 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: I809e53c4e3449a45ecd1fdec260986011b88206e
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>