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Change-Id: Ic6d21ee8dde3cb443319436a50289ddf5b5bbc56
build: qcom: Set QCOM_*_PATH variables for hardware/qcom-* projects

This consolidates a bunch of one-off logic scattered throughout the
code base.  Usage in Android.mk files is trivial:

At top level, use e.g. "ifeq ($(call my-dir),$(QCOM_AUDIO_PATH))".
This works for all variants, including non-variants (i.e. AOSP).

Within subdirs, use e.g. hardware/qcom/audio => $(QCOM_AUDIO_PATH)

Change-Id: Iee2497ea9a7efeb4ae9e861b84c532b19da7b69d