qcom_target: Remove unused support for CAF manifests

* This code was introduced to support building from Qualcomm hardware
  manifests, placing the appropriate Qualcomm HALs at the AOSP
  hardware/qcom/$(HAL_TYPE) location. This isn't a supported use case
  anymore, so remove the dead code.

Change-Id: Id7d53b33f53289bc1ead8eb983d7e252940b0387