x mutex debug code for wrong loop termination value

Loop was terminating one iteration early, missing one of the
debugger handshake mutexes. Linn Crosetto.

Signed-off-by: Bob Moore <robert.moore@intel.com>
Signed-off-by: Lin Ming <ming.m.lin@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>
Signed-off-by: Andi Kleen <ak@linux.intel.com>