universal8890: audio: remove redundant controls

  * AIF4TX1 Input 1 Volume and AIF4TX1 Input 2 Volume are redundant in
    gain-incall_wb-speaker and gain-incall_nb-speaker.
    In fact, voice-speaker and voice-speaker-wb paths already include
    incall_nb-speaker and incall_wb-speaker which in turns includes
    unmute-speaker path which already sets AIF4TX1 Input 1 Volume and
    AIF4TX1 Input 2 Volume.

  * Note that this does not break the path speaker-and-headphones as it
    inherits gain-media-speaker-headset where AIF4TX1 Input 1 Volume
    and AIF4TX1 Input 2 Volume are set

Change-Id: Iac92f51eedff0e0a3f9db63138718b29397db2fa