lsm: update the BUILD_BUG_ON() in audit_log_lsm_data()

On 32-bit systems the newly added namespace fields in the
common_audit_data struct exceed the BUILD_BUG_ON(sizeof(void *) * 2)
size check in audit_log_lsm_data().  Convert the size check to two
u64 types to both fit the new fields and move to a size that is not
architecture dependent.

Fixes: bb20ca26f960 ("lsm: add LSM_AUDIT_DATA_NS for namespace audit records")
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202608131232.Owej9tlx-lkp@intel.com/
Signed-off-by: Paul Moore <paul@paul-moore.com>

security/lsm_audit.c

@@ -182,7 +182,7 @@ void audit_log_lsm_data(struct audit_buffer *ab,
 	 * start making this union too large!  See struct lsm_network_audit
 	 * as an example of how to deal with large data.
 	 */
-	BUILD_BUG_ON(sizeof(a->u) > sizeof(void *)*2);
+	BUILD_BUG_ON(sizeof(a->u) > (sizeof(u64) * 2));
 
 	switch (a->type) {
 	case LSM_AUDIT_DATA_NONE: