KVM: selftests: Convert vgic_irq away from VCPU_ID

Convert vgic_irq to use vm_create_with_one_vcpu() and pass around a
'struct kvm_vcpu' object instead of passing around a vCPU ID (which is
always the global VCPU_ID...).

Opportunstically align the indentation for multiple functions'
parameters.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>