net: Revert "net: optimize the sockptr_t for unified kernel/user address spaces"

net: Revert "net: optimize the sockptr_t for unified kernel/user address spaces"

This reverts commits 6d04fe15f78acdf8e32329e208552e226f7a8ae6 and
a31edb2059ed4e498f9aa8230c734b59d0ad797a.

It turns out the idea to share a single pointer for both kernel and user
space address causes various kinds of problems.  So use the slightly less
optimal version that uses an extra bit, but which is guaranteed to be safe
everywhere.

Fixes: 6d04fe15f78a ("net: optimize the sockptr_t for unified kernel/user address spaces")
Reported-by: Eric Dumazet <edumazet@google.com>
Reported-by: John Stultz <john.stultz@linaro.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: David S. Miller <davem@davemloft.net>