selftests/mm: define types using typedef in pkey-helpers.h

Using #define to define types should be avoided. Use typedef instead.
Also ensure that __u* types are actually defined by including
<linux/types.h>.

Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Kevin Brodsky <[e-mail]>
Cc: Aruna Ramakrishna <[e-mail]>
Cc: Catalin Marinas <[e-mail]>
Cc: Dave Hansen <[e-mail]>
Cc: Joey Gouly <[e-mail]>
Cc: Keith Lucas <[e-mail]>
Cc: Ryan Roberts <[e-mail]>
Cc: Shuah Khan <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>

tools/testing/selftests/mm/pkey-helpers.h

···
 #include <ucontext.h>
 #include <sys/mman.h>
 
+#include <linux/types.h>
+
 #include "../kselftest.h"
 
 /* Define some kernel-like types */
-#define  u8 __u8
-#define u16 __u16
-#define u32 __u32
-#define u64 __u64
+typedef __u8	u8;
+typedef __u16	u16;
+typedef __u32	u32;
+typedef __u64	u64;
 
 #define PTR_ERR_ENOTSUP ((void *)-ENOTSUP)