internal/socket: remove leftover AF_* and SOCK_RAW constants on aix

Follow-up for CL 53310 which changed internal/socket to use these
constants from golang.org/x/sys/unix

Change-Id: I40fde84c875995fbeef2d21f8e05f5ba27b11098
Reviewed-on: https://go-review.googlesource.com/c/net/+/178557
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

internal/socket/defs_aix.go

@@ -16,14 +16,6 @@ package socket
 */
 import "C"
 
-const (
-	sysAF_UNSPEC = C.AF_UNSPEC
-	sysAF_INET   = C.AF_INET
-	sysAF_INET6  = C.AF_INET6
-
-	sysSOCK_RAW = C.SOCK_RAW
-)
-
 type iovec C.struct_iovec
 
 type msghdr C.struct_msghdr