KVM: x86: use array_index_nospec with indices that come from guest

KVM: x86: use array_index_nospec with indices that come from guest

min and dest_id are guest-controlled indices. Using array_index_nospec()
after the bounds checks clamps these values to mitigate speculative execution
side-channels.

Signed-off-by: Thijs Raymakers <thijs@raymakers.nl>
Cc: stable@vger.kernel.org
Cc: Sean Christopherson <seanjc@google.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Fixes: 715062970f37 ("KVM: X86: Implement PV sched yield hypercall")
Fixes: bdf7ffc89922 ("KVM: LAPIC: Fix pv ipis out-of-bounds access")
Fixes: 4180bf1b655a ("KVM: X86: Implement "send IPI" hypercall")
Link: https://lore.kernel.org/r/20250804064405.4802-1-thijs@raymakers.nl
Signed-off-by: Sean Christopherson <seanjc@google.com>