socket: move compat timeout handling into sock.c

This is a cleanup to prepare for the addition of 64-bit time_t
in O_SNDTIMEO/O_RCVTIMEO. The existing compat handler seems
unnecessarily complex and error-prone, moving it all into the
main setsockopt()/getsockopt() implementation requires half
as much code and is easier to extend.

32-bit user space can now use old_timeval32 on both 32-bit
and 64-bit machines, while 64-bit code can use
__old_kernel_timeval.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Deepa Dinamani <deepa.kernel@gmail.com>
Acked-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>