ofproto-dpif-upcall: Use atomic_long in struct udpif

Some concern has been raised by Ben Pfaff that atomic_uint64_t may not
be portable. Accordingly, use atomic_ulong instead of atomic_uint64_t
in struct ofproto.

This is in preparation for removing atomic_uint64_t entirely.

Cc: YAMAMOTO Takashi <yamamoto@valinux.co.jp>
Signed-off-by: Simon Horman <horms@verge.net.au>
Signed-off-by: Ben Pfaff <blp@nicira.com>
ovs-atomic: Remove atomic_uint64_t and atomic_int64_t.

Some concern has been raised by Ben Pfaff that atomic_uint64_t may not
be portable. In particular on 32bit platforms that do not have atomic
64bit integers.

Now that there are no longer any users of atomic_uint64_t remove it
entirely. Also remove atomic_int64_t which has no users.

Cc: YAMAMOTO Takashi <yamamoto@valinux.co.jp>
Signed-off-by: Simon Horman <horms@verge.net.au>
Signed-off-by: Ben Pfaff <blp@nicira.com>