registerService

為了要讓clients可以找到driver，
要先呼叫registerService()

ex:
有個driver com_MySoftwareCompany_driver_SampleINQUIRYDriver，
在它的start function呼叫registerService()

bool com_MySoftwareCompany_driver_SampleINQUIRYDriver::start(IOService* provider)
{
bool success;

IOLog("SampleINQUIRYDriver::start()\n");

success = super::start(provider);

if (success) {
// Publish ourselves so clients can find us
registerService();
}

return success;
}