qemu: properly free addresses on non-serial chardev unplug
The target type comparison in qemuDomainDetachChrDevice
used the VIR_DOMAIN_CHR_SERIAL_TARGET_TYPE enum, so virtio-serial
addresses were not freed properly for channel devices.
Call qemuDomainReleaseDeviceAddress uncoditionally and decide
based on the address type instead of the target/device types.