topology:pre-process-object: merge object config with parent object config

topology:pre-process-object: merge object config with parent object config

An object can be declared within a class definition as follows:

Class.Pipeline.volume-playback {
	Object.Widget.pga.0 {
		ramp_step_ms 250
	}
}

While instantiating the volume-pipeline class, the pga object
could be modified as follows:

Object.Pipeline.volume-playback.0 {
	Object.Widget.pga.0 {
		format "s24le"
	}
}

When building the pga.0 object in the class definition, merge
the attributes declared in the volume-playback.0 object to create
a new config as follows to make sure that all attributes are
set for the pga object.

	Object.Widget.pga.0 {
		ramp_step_ms 250
                format "s24le"
        }

Signed-off-by: Ranjani Sridharan <ranjani.sridharan@linux.intel.com>
Signed-off-by: Jaroslav Kysela <perex@perex.cz>