testbench_fp has part selects out of bounds

[davidharrishmc]

$ wsim fd_ieee_rv64gc all --tb testbench_fp

produces warnings such as

# ** Warning: /home/harris/cvw/testbench/testbench_fp.sv(1053): (vopt-2697) MSB 519 of part-select into 'TestVector' is out of bounds.
# ** Warning: /home/harris/cvw/testbench/testbench_fp.sv(780): (vopt-2697) MSB 126 of part-select into 'Ans' is out of bounds.
# ** Warning: /home/harris/cvw/testbench/testbench_fp.sv(780): (vopt-2697) MSB 111 of 
# ** Warning: /home/harris/cvw/testbench/testbench_fp.sv(801): (vopt-2697) MSB 126 of part-select into 'Res' is out of bounds.
# ** Warning: /home/harris/cvw/testbench/testbench_fp.sv(909): (vopt-2697) MSB 110 of part-select into 'X' is out of bounds.

[davidharrishmc]

Fixed with PR #791