This fixes a Spectre-v1/L1TF vulnerability in picdev_write().
It replaces index computations based on the (attacked-controlled) port
number with constants through a minor refactoring.

Fixes: 85f455f7 ("KVM: Add support for in-kernel PIC emulation")
Signed-off-by: NNick Finco <nifi@google.com>
Signed-off-by: NMarios Pomonis <pomonis@google.com>
Reviewed-by: NAndrew Honig <ahonig@google.com>
Cc: stable@vger.kernel.org
Reviewed-by: NJim Mattson <jmattson@google.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>