cpukit/stackchk: Remove additional offset of SANITY_PATTERN_SIZE_WORDS

This offset is already accounted for by Stack_check_Usable_stack_start()
called from Stack_check_Visit_stack() and adding it a second time can
cause interaction beyond the bounds of the stack.

cpukit/libmisc/stackchk/check.c

@@ -409,7 +409,6 @@ static inline void *Stack_check_Find_high_water_mark(
      * match pattern
      */
 
-    base += SANITY_PATTERN_SIZE_WORDS;
     for (ebase = base + length; base < ebase; base++)
       if (*base != U32_PATTERN)
         return (void *) base;