nm_match_spec_device_by_pllink() does not support matching on all parameters,
unlike nm_match_spec_device(). The reason is that certain parameters are
only available when having a NMDevice instance.

Add an argument "match_device_type", so that the caller can inject the
device type to be used. Note that for NMDevice, the device-type is
nm_device_get_type_description(), which usually depends on the device
class only. The only caller of nm_match_spec_device_by_pllink() is the
wifi factory, and it already knows that it wants to create a device of
type NMDeviceWifi. Hence, it knows and can specify "wifi" as
match_device_type.