Revert "coredump: Remove the WARN_ON in dump_vma_snapshot"

This reverts commit 7ba958df64.

It breaks the kernel abi so revert it for now.  We will add it back
later at the next kabi update.

Bug: 161946584
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
Change-Id: I594a8403ac897c8aef507f7421ed8ff80935b267

fs/coredump.c

@@ -1151,6 +1151,12 @@ static bool dump_vma_snapshot(struct coredump_params *cprm)
 
 	mmap_write_unlock(mm);
 
+	if (WARN_ON(i != cprm->vma_count)) {
+		kvfree(cprm->vma_meta);
+		return false;
+	}
+
+
 	for (i = 0; i < cprm->vma_count; i++) {
 		struct core_vma_metadata *m = cprm->vma_meta + i;