coredump: Remove the WARN_ON in dump_vma_snapshot

The condition is impossible and to the best of my knowledge has never
triggered.

We are in deep trouble if that conditions happens and we walk past
the end of our allocated array.

So delete the WARN_ON and the code that makes it look like the kernel
can handle the case of walking past the end of it's vma_meta array.
Reviewed-by: NJann Horn <jannh@google.com>
Reviewed-by: NKees Cook <keescook@chromium.org>
Signed-off-by: N"Eric W. Biederman" <ebiederm@xmission.com>

fs/coredump.c

@@ -1139,12 +1139,6 @@ 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;