UAPI: Fix AHZ multiple inclusion when __KERNEL__ is removed

Fix AHZ multiple inclusion when __KERNEL__ is removed as part of the separation
of the userspace headers from the kernel headers.
Signed-off-by: David Howells <dhowells@redhat.com>

include/linux/acct.h

@@ -146,6 +146,9 @@ extern void acct_exit_ns(struct pid_namespace *);
  *
  */
 
+#undef ACCT_VERSION
+#undef AHZ
+
 #ifdef CONFIG_BSD_PROCESS_ACCT_V3
 #define ACCT_VERSION	3
 #define AHZ		100