staging: prima: Fix non-debug build and switch to it

Enable the forward declaration of debug functions in non-debug
builds and disable a piece of code used only to print some info.
-Wno-unused-variable is now required because of all the variables
used in debug functions that aren't left out in non-debug builds.

Change-Id: I7069f8859e4965ee82ce65c29c35349c887fd673