KVM: Protect in-kernel pio using kvm->lock

pio operation and IRQ_LINE kvm_vm_ioctl is not kvm->lock
protected.  Add lock to same with IOAPIC MMIO operations.

Signed-off-by: Yaozu (Eddie) Dong <eddie.dong@intel.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>