coredump: Remove the WARN_ON in dump_vma_snapshot

coredump: Remove the WARN_ON in dump_vma_snapshot

commit 49c1866348f364478a0c4d3dd13fd08bb82d3a5b upstream.

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: Jann Horn <jannh@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>