lsm: align based on pointer length in lsm_fill_user_ctx()

Using the size of a void pointer is much cleaner than
BITS_PER_LONG / 8.

Acked-by: Casey Schaufler <[e-mail]>
Signed-off-by: Paul Moore <[e-mail]>

security/security.c

···
 	size_t nctx_len;
 	int rc = 0;
 
-	nctx_len = ALIGN(struct_size(nctx, ctx, val_len), BITS_PER_LONG / 8);
+	nctx_len = ALIGN(struct_size(nctx, ctx, val_len), sizeof(void *));
 	if (nctx_len > *uctx_len) {
 		rc = -E2BIG;
 		goto out;