atm: Cleanup atm_tcp.h and atm.h for userspace.

The atm_tcp.h uses types from linux/atm.h, but does not include it.
It should also use the standard __u## types from linux/types.h rather
than the uint##_t types since the former can be found with the kernel
already.

Same goes for linux/atm.h.  The linux/socket.h include there also gets
dropped as atm.h does not actually use anything from socket.h.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: David S. Miller <davem@davemloft.net>