boards:make: hardcode goodfet.bsl path in Makefile.include

@all: 
Did anybody (successfully) used TelosB or Z1 with an other version of goodfet.bsl than that shipped with RIOT? 
At least for the TelosB this lead to errors for me and others (#1438) so I'd propose use RIOT's goodfet in Makefiles for TelosB and Z1. Any opinions on this?