This patch passes struct kvm_pit into internal PIT functions.
Those functions used to get PIT through kvm->arch.vpit, even though most
of them never used *kvm for other purposes.  Another benefit is that we
don't need to set kvm->arch.vpit during initialization.
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>