cpukit/posix: Fix uninitialized read in sem_open (CID 1667263)

Note: This fix was analyzed and implemented manually based
on the Coverity report.

cpukit/posix/src/semopen.c

@@ -128,7 +128,7 @@ sem_t *sem_open(
   va_list                   arg;
   unsigned int              value = 0;
   POSIX_Semaphore_Control  *the_semaphore;
-  size_t                    name_len;
+  size_t                    name_len = 0;
   Objects_Get_by_name_error error;
   sem_t                    *sem;