Add missing dependencies to cbordump build

Compilation was failing when trying to compile cbordump running make in
tools directory. Add missing dependencies, cbortojson and
cborparser_dup_string to cbordump Makefile.

Signed-off-by: Otavio Pontes <otavio.pontes@intel.com>
Signed-off-by: Thiago Macieira <thiago.macieira@intel.com>