UAPI: fix tools/vm/page-types.c

Fix tools/vm/page-types.c to use the UAPI variant of linux/kernel-page-flags.h
lest the following error appear:

  In file included from page-types.c:38:0:
    ../../include/linux/kernel-page-flags.h:4:42: fatal error:
    uapi/linux/kernel-page-flags.h: No such file or directory

Reported-by: Daniel Hazelton <dshadowwolf@gmail.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Fengguang Wu <fengguang.wu@intel.com>
Tested-by: Daniel Hazelton <dshadowwolf@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>