Multi-uORB support changes - part 1

This adds support for a dynamic build for QuRT and initial
Multi-uORB changes to enable communication between the DSP and
the application processor.

This part of the changes do not affect the POSIX build. This is
enablement for the QuRT build using Multi-uORB. The second part
of the changes will be added in a new module under src/modules.

Signed-off-by: Mark Charlebois <charlebm@gmail.com>