um: -include user.h for USER_OBJ, trim includes

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Richard Weinberger <richard@nod.at>

arch/um/os-Linux/aio.c

@@ -11,10 +11,8 @@
 #include <asm/unistd.h>
 #include "aio.h"
 #include "init.h"
-#include "kern_constants.h"
 #include "kern_util.h"
 #include "os.h"
-#include "user.h"
 
 struct aio_thread_req {
 	enum aio_type type;