build: Reorganize inclusion of QCOM macros

* There's actually not a whole lot QC-specific about these macros,
  make them available at definition.mk inclusion time rather than
  relying on BoardConfig to include them.
* Don't create a dependency on QCOM macros from a makefile
  that is included very early in the build process.

Change-Id: I3dcaf0e068ca44732cfe58f69384621781ddda67