hal: Avoid unnecessary rerouting for sample rate changes

 * The backend codec supports just a few sample rates directly,
   so make sure that we base our decision to reroute on this
   value instead of the actual sample rate of the stream.

Change-Id: I2ed82354563f60d04febb0e200252d0f45644a5e
Merge branch 'cm-11.0' of https://github.com/CyanogenMod/android_hardware_qcom_audio-caf into cm-11.0