selftests/mm: fix build warnings on ppc64

Fix warnings like:

In file included from uffd-unit-tests.c:8:
uffd-unit-tests.c: In function `uffd_poison_handle_fault':
uffd-common.h:45:33: warning: format `%llu' expects argument of type
`long long unsigned int', but argument 3 has type `__u64' {aka `long
unsigned int'} [-Wformat=]

By switching to unsigned long long for u64 for ppc64 builds.

Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Michael Ellerman <[e-mail]>
Cc: Shuah Khan <[e-mail]>
Cc: <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>

tools/testing/selftests/mm/gup_test.c

···
+#define __SANE_USERSPACE_TYPES__ // Use ll64
 #include <fcntl.h>
 #include <errno.h>
 #include <stdio.h>

tools/testing/selftests/mm/uffd-common.h

···
 #define __UFFD_COMMON_H__
 
 #define _GNU_SOURCE
+#define __SANE_USERSPACE_TYPES__ // Use ll64
 #include <stdio.h>
 #include <errno.h>
 #include <unistd.h>