Drop the unused @vcpu parameter from hwapic_isr_update().  AMD/AVIC is
unlikely to implement the helper, and VMX/APICv doesn't need the vCPU as
it operates on the current VMCS.  The result is somewhat odd, but allows
for a decent amount of (future) cleanup in the APIC code.

No functional change intended.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20220614230548.3852141-3-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>