vect: Remove always-true condition

vect: Remove always-true condition

vectorizable_reduction had code guarded by:

  if (STMT_VINFO_DEF_TYPE (stmt_info) == vect_reduction_def
      || STMT_VINFO_DEF_TYPE (stmt_info) == vect_double_reduction_def)

But that's always true after:

  if (STMT_VINFO_DEF_TYPE (stmt_info) != vect_reduction_def
      && STMT_VINFO_DEF_TYPE (stmt_info) != vect_double_reduction_def
      && STMT_VINFO_DEF_TYPE (stmt_info) != vect_nested_cycle)
    return false;

  if (STMT_VINFO_DEF_TYPE (stmt_info) == vect_nested_cycle)
    {
      …
      return true;
    }

(I wasn't sure at first how the empty “else” for the first “if” above
was supposed to work.)

gcc/
	* tree-vect-loop.c (vectorizable_reduction): Remove always-true
	if condition.