x86/speculation: Add Ivy Bridge to affected list

commit 3798cc4d106e91382bfe016caa2edada27c2bb3f upstream

Make the docs match the code.

Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>