restorer: Round size of area with self vmas up to page size

These chunks of memry, which transit into restorer code gets unmapped one-by-one and thus each of them
should be page-aligned.
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

cr-restore.c

@@ -1495,7 +1495,7 @@ static int sigreturn_restore(pid_t pid)
 	if (ret < 0)
 		goto err;
 
-	self_vmas_len = (ret + 1) * sizeof(*self_vma);
+	self_vmas_len = round_up((ret + 1) * sizeof(*self_vma), PAGE_SIZE);
 
 	/* pr_info_vma_list(&self_vma_list); */