Revert "audio_route: fix possible segfault"

This reverts commit 84f0b1899302784c679105f444e87686a66c1274.

Change-Id: I35c375d7b8291eca166267f621f6ef4d4b870a1c
audio_route: fix crash with unsupported control types

Check if control type is supported before accessing xxx_value
fields in mixer_state structure.

Also remove unused parameter warning.

Change-Id: I9005d4760e55f0798d576bd4507700e198900311