[NET]: Revert socket.h/stat.h ifdef hacks.

This reverts 57a87bb0.

As H. Peter Anvin states, this change broke klibc and it's
not very easy to fix things up without duplicating everything
into userspace.

In the longer term we should have a better solution to this
problem, but for now let's unbreak things.

Signed-off-by: David S. Miller <davem@davemloft.net>